PT340 Improving international competitiveness of the French fry potato industry in SE South Australia

Paul Frost Primary Industries SA

PT340

This report is published by the Horticultural Research and Development Corporation to pass on information concerning horticultural research and development undertaken for the potato industry.

The research contained in this report was funded by the Horticultural Research and Development Corporation with the financial support of Safries Pty Ltd.

All expressions of opinion are not to be regarded as expressing the opinion of the Horticultural Research and Development Corporation or any authority of the Australian Government.

The Corporation and the Australian Government accept no responsibility for any of the opinions or the accuracy of the information contained in this report and readers should rely upon their own enquiries in making decisions concerning their own interests.

Cover price: $20.00 HRDC ISBN 1 86423 625 6

Published and distributed by: Horticultural Research & Development Corporation Level 6 7 Merriwa Street Gordon NSW 2072 Telephone: (02) 9418 2200 Fax: (02) 9418 1352 E-Mail: hrdc@hrdc.gov.au

© Copyright 1997

HRDVC

HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION

Partnership in horticulture

Contents

Industry Summary

Technical Summary

Introduction

Management of the Service

Services Provided in the 1995/96 Season

Outcomes

Benefits of PCMS

Directions for Future Research

Other Pubiicationsfrom the Project

Acknowledgments

Appendix 1 - Extract from Benefit Cost Analysis

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Industry Summary

The potato crop management service (PCMS) commenced operations in July 1993. PCMS is a modular crop management service assisting growers to adopt the latest technology on a fee for service basis. The general aim of the service was to improve the international competitiveness of the french fry industry in south eastern Australia by the uptake of technology for improved yield and quality.

Specific objectives of PCMS were : • To develop a new approach to technology transfer which incorporates a level of industry

ownership and control and to structure that service to minimise dependency on government extension services.

• To raise the average yield of potatoes for french fry processing by 10% over 3 years in the south east of South Australia and western Victoria.

• To improve the quality of tubers in general, and to reduce the risk of crops being rejected for processing.

• To ensure that technology packages for potato growers are relevant, provide favourable benefit/cost to clients, and are constantly updated with results from research and development projects.

Services provided: PCMS has been provided to potato growers in the S.E. for the past 3 seasons. In the 1995/96 season, PCMS provided plant nutrition, irrigation and crop monitoring services to 64 separate potato "variety blocks", covering 1,220 ha (3,010 acres) with direct fees collected from growers of more than $100,000. The farm gate value of the crops managed in 1995/96 was more than $10 million and represents >50% of the area planted to potatoes in the S.E. of the state.

Resources, Management & Staff Development The service has been supported financially by PISA, HRDC, McCain Foods and the potato growers in the south east of South Australia. PCMS is managed by PISA in close consultation with a steering committee. The steering committee consists of 2 potato growers, Safries Field Department Manager, and key PISA staff.

Staff training and development has been a high priority. Mr. Heap has completed two study tours of potato research, industry and consultants operating in the north west of the USA (1993 & 1994). Mr. Frost (Industry Development Officer employed by the project) undertook a study tour examining potato production & research in the Ballarat area & Northern Tasmania.

Future Developments • PCMS is developing new approaches to trace element nutrition, aiming to improve crop

growth by pre-emptive actions. • Electronic weather stations are to be developed to assist with accurate forecasting of

disease outbreaks and crop water use. • Plans are being developed to link growers, processors, researchers and PCMS

through an easy to use computer network. Development of computer software that enables the provision of high quality services at the lowest cost possible continues.

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Technical Summary

Outcomes - Impact on crop management

The majority of clients have indicated that they believe that the input of PCMS has improved their crop management skills. All enterprises have benefitted from comprehensive records and access to pooled data from all crops. The impact of PCMS on crop management practices was greatest in 1995/96 as growers gained confidence in the quality of service provided by PCMS and as a new pre-emptive philosophy was applied to all of the service modules.

Some notable general changes to crop management as a result of PCMS were : • Improved plant nutrition, especially the correction of trace element deficiencies with broad-

acre spray application of cheap sulfate forms to the soil before planting and the timely correction of emerging deficiencies in the growing crop by foliar sprays.

• Examination and improvement of crop establishment and irrigation practices. • Awareness of diseases (particularly pink rot and target spot) and integrated approaches to

control. • The widespread recording of important crop management operations, a great help in

reviewing crop performance and planning future strategies for each enterprise. • Creation of a crop production data base to assist with industry research and development

issues.

Outcomes - Research

The collective analysis of records from 55 crops managed in 1993/94, 95 crops managed in 1994/95 and 64 crops managed in 1995/96 has provided valuable insights into all aspects of potato agronomy. Technical areas to benefit from this analysis include :

• The interaction between irrigation and N, P & K nutrition and chloride toxicity • Fine tuning fertiliser strategies for different varieties and soil types • Maintenance of trace element nutrition • The interaction between target spot and plant nutrition • Plant population and yield • Seed physiological age and crop performance • Production economics • Potential new production systems for potatoes on sandy soils

Outcomes - Industry Servicing

PCMS has allowed PISA to provide a comprehensive service to south east potato growers at a time of declining resources. The employment and training of additional staff has enhanced the skills base working for the benefit of the potato industry.

Recommendations:

1. HRDC support (in principle) the utilisation (and further improvement) of PCMS software and concepts by service providers to horticulture.

2. HRDC support forthcoming project submissions which seek to build on the significant development momentum generated by PCMS in the SE potato industry .

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Introduction

The main outcome from this project was the development and delivery of:-

Potato Crop Management Service (PCMS)

PCMS commenced operations in July 1993,

PCMS is a modular crop management service assisting growers to adopt the latest technology on a fee for service basis. The general aim of the service is to improve the international competitiveness of the french fry industry in south eastern Australia by the uptake of technology for improved yield and quality.

The technology for high yield and quality potato production has become more complex during a period when extension strategies have moved towards mass and group methods. The resolution of crop yield and quality issues requires complex crop management decisions based on advanced approaches to crop monitoring and 1:1 consultation with growers.

Specific objectives of PCMS are :

• To develop a new approach to technology transfer which incorporates a level of industry ownership and control and to structure that service to minimise dependency on government extension services.

• To raise the average yield of potatoes for french fry processing by 10% over 3 years in the south east of South Australia and western Victoria.

• To improve the quality of tubers in general, and to reduce the risk of crops being rejected for processing.

• To ensure that technology packages for potato growers are relevant, provide favourable benefit/cost to clients, and are constantly updated with results from research and development projects.

The service has been supported financially by PISA, HRDC, McCain Foods and the potato growers in the south east of South Australia.

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Management of the Service

PCMS is managed by PISA in close consultation with a steering committee. The steering committee consists of:

• Mr. T. Heysen & Mr. F. Young (potato growers) • Mr. G. Henman (Safries/McCain Foods) • Mr. M. Heap, Mr. B. Philp & Mr. P. Frost (PISA)

The steering committee concept has worked very well, with constructive debate on issues such as financial management, staff development, technical development of modules, and grower and processor feedback. Seven meetings have been held.

Staff of PCMS have included :

• Mr. Mark Heap B.Ag.Sc.(Hons) MSc. • Mr. Paul Frost B.Ag.Sc. • Mr. Derek Cameron B.Ag.Sc. • Mr. David Moss R.D.A. • Ms. Sue Black B.Sc. D.App.Sc. • Ms. Terri Hollenberg D.App.Sc.

Messrs. Heap and Frost are responsible for the day to day conduct of the service and technical development. Mr Frost replaced Mr Cameron, who resigned from the position in 1994. Mr Moss, a person with previous experience in the south east potato industry, has been employed to assist with crop scouting, sample collection and field staff training during periods of peak activity. Ms. Black and Ms. Hollenberg have been trained to perform crop scouting, sample collection and report preparation during periods of peak activity.

Staff training and development has been a high priority. Mr Frost is about to undertake a study tour examining potato production and research in the Ballarat area and in Northern Tasmania. Mr. Heap has completed two study tours of potato research, industry and consultants operating in the north west of the USA (1993 & 1994).

Specialist researchers within PISA and SARDI have been used extensively to supplement local expertise, particularly in the fields of plant pathology, nutrition and irrigation.

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Services provided in the 1995/96 season.

The response amongst growers to the new service was positive, and PCMS provided plant nutrition, irrigation and crop monitoring services to 64 separate potato "variety blocks" covering 1,220 ha (3,010 acres) with direct fees collected from growers of more than $100,000 1995/96. The farm gate value of the crops managed in 1995/96 was more than $10 million and represents more than 50% of the area planted to potatoes in the south east of the state.

Three groups of services were provided :

Plant Nutrition

• Pre-plant soil analysis - P, K, Cu, Zn, Mn, Fe, pH, salinity, organic carbon, water repellence.

• Quality soil analysis report, interpretation and advice

• Pre-plant discussion to assist with the planning of fertiliser applications and weed control.

• A minimum of 5 petiole samples per crop for macro and micro element analysis - N, P, K,

Mg, Ca, Cu, Zn, Mn, Fe, CI. Turn-around time 3 days.

• Quality petiole analysis reports, interpretation and advice.

• End of year summary of plant nutrition, with notes on future fertiliser programs.

Crop monitoring

• Pre-plant discussion to assist with the planning of weed, pest and disease control.

• Weekly inspection for crop appearance, tuber development and quality, pests, diseases,

weeds and soil moisture.

• Detailed report produced 'on the spot' providing management options.

• Professional plant pathology and entomology back-up when needed.

• End of year summary, including reports on tuber quality, number and size, weed, pest and

disease levels, comparisons with district averages, and notes on future improvements.

Irrigation scheduling

• Pre-plant laboratory analysis of soil to determine it's moisture holding characteristics.

• Pre-plant discussion to assist with general crop irrigation approach & irrigation equipment.

• Provision of a compact computer (programmed to assist with irrigation decisions) and a

class A evaporation pan (electronic weather station in one region).

• Weekly soil coring and regular crop & soil inspections to support computer aided decisions.

• End of year summary of irrigation operations, including graphs showing the amount and timing of water applied, seasonal soil moisture levels, and notes on future improvements.

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Additional Service Developed: Service Calendar

In addition to the service modules, growers received:

1. Pre-planting crop production planning advice.

In this session, information is collected to assist with site selection, identification of potential problems and crop management strategies in nutrition, irrigation and pest & disease control. The pre-planting process culminates in the production of a chronological checklist - "On Track & On Time" which is supplied to growers for each variety block within a week of sowing. "On Track & On Time" is a computer-generated template which lists strategies, timing of each activity and the type & rate of fertilisers or chemicals to be used.

2. Post-harvest review of season performance.

At the end of each season, growers are supplied with a report which provides a summary, analysis and comments for each of the service modules, and a regional overview.

Funding details:

The development of the service described in this Final Report was funded by the Horticultural Research and Development Corporation, with the financial support of McCain Foods.

Year Voluntary Total Project Contribution Cost

1993/94 $32,125 $64,250 1994/95 $28,266 $56,532 1995/96 $25,077.5 $50,155

Growers paid on a fee-for-service basis, to support the delivery of the service developed. Direct fees collected from growers in 1995/96 exceeded $ 100,000.

The service ran well within budget in each of the three years of operation.

A consultant was engaged in early 1995 to examine the business and financial structure of PCMS and to flag changes for the long term health of the service. This study identified a need for review of the fee system, to examine key areas of high cost, and to develop options for new business structures.

The development of the concept where growers and processors take a financial and management stake in the provision of their own advisory services has taken an enormous leap forward. The future provision of strong and relevant crop management services to the potato industry of south eastern Australia can only be assured by this approach.

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Outcomes

Outcomes - Impact on crop management

All of the commitments made by PCMS to growers were met or exceeded, including :

• Number of petiole and soil samples • Turn around times for laboratory analysis and reporting • Reporting standards • Timely advice using the best available technology

The impact of PCMS on crop management practices varied between growers. No instances are known where advice/input from PCMS has been implicated in poor crop performance. The majority of clients have indicated that they believe that the input of PCMS has improved their crop management skills. All enterprises have benefitted from comprehensive records and access to pooled data from all crops.

The impact of PCMS on crop management practices was greatest in 1995/96 as growers gained confidence in the quality of service provided by PCMS and as a new pre-emptive philosophy was applied to all of the service modules.

Some notable general changes to crop management as a result of PCMS were :

• Improved plant nutrition, especially the correction of trace element deficiencies with broad-acre spray application of cheap sulfate forms to the soil before planting and the timely correction of emerging deficiencies in the growing crop by foliar sprays.

• Examination and improvement of crop establishment and irrigation practices.

• Awareness of diseases (particularly pink rot and target spot) and integrated approaches to control.

• The widespread recording of important crop management operations, a great help in reviewing crop performance and planning future strategies for each enterprise.

• Creation of a crop production data base to assist with industry research and development issues.

Outcomes - Research

A large effort has gone into the production of comprehensive end of year summaries for each crop monitored by PCMS (about 20 pages per crop). This approach is looking to the longer term, where benefits from records collected by the service may outweigh those gained in this season. The collective analysis of records from 55 crops managed in 1993/94, 95 crops managed in 1994/95 and 64 "variety blocks" managed in 1995/96 has provided valuable insights, representing a "value for money" research facility for the potato industry of south eastern Australia. Technical areas to benefit from this analysis include :

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The interaction between irrigation and N, P & K nutrition and chloride toxicity Fine tuning fertiliser strategies for different varieties and soil types Maintenance of trace element nutrition The interaction between target spot and plant nutrition Plant population and yield Seed physiological age and crop performance Production economics Potential new production systems for potatoes on sandy soils

Outcomes - PISA

PCMS has allowed PISA to provide a comprehensive service to south east potato growers at a time of declining resources. Plans are being made for future use (and probable expansion) of PCMS concepts and intellectual property by other service providers to horticulture. The employment and training of additional staff has enhanced the skills base working for the benefit of the potato industry.

The partnership between industry (processors and growers) and PISA has clearly focussed the efforts of PISA on industry needs. In particular the steering committee has been a valuable and powerful tool in this process.

This service has greatly increased the economic benefit of PISA to the state by increasing the international competitiveness of potato growers. The reputation of the region as a supplier of quality tubers will continue to grow with the professional approach employed by growers. The reliability and efficiency of the potato industry of south eastern South Australia is a critical factor in 3 large developments currently being considered :

• McCain Foods are looking to increase the capacity of the french fry factory at Penola. • A second major food processor is looking to build a large french fry factory in the region. • A group is examining the prospects of growing and packing ware potatoes in the south east

for export to the rapidly expanding potato markets of Asia.

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Benefits of PCMS

38 t/ha. 47 t/ha. 41 t/ha.

37.5 t/ha 37.5 t/ha 45 t/ha 50 t/ha 50 t/ha

Clients PCMS has certainly developed a new approach to technology transfer which incorporates a level of industry ownership and control.

Support for the service from growers and processors has been strong. An independent report by a private consultant was engaged in early 1995, found that growers (particularly new growers) were impressed by the advice offered by the service. The study found that overall, most growers believe the service focusses on the right areas, and growers are almost certainly paying more attention to their crops than before.

Yield The 5 year average yield amongst potato growers in the S.E. prior to the commencement of PCMS, was: In 1993/94, average yields for growers subscribing to PCMS were: In 1994/95, average yields for growers subscribing to PCMS were: In 1994/95, average yields for growers subscribing to PCMS were:

Pontiac Coliban Shepody Kennebec Russet Burbank

Thus over the past 3 years, PCMS has significantly contributed to a yield increase in excess of 10 t/ha - for Russet Burbank's grown in the S.E.

Quality Safries (McCain) process approximately 60,000t of potatoes at Penola, with a farm gate value of approximately $12 million. Safries estimate that an increase in "recovery" of 2% has been achieved since the commencement of PCMS. No data is available on the fresh market crop.

A Benefit Cost analysis of this project was performed using the REVS Version 2.0 software. Key information from this analysis is presented in Appendix 1.

Directions for Future Research

PCMS is developing new approaches to trace element nutrition, aiming to improve crop growth by pre-emptive actions.

Electronic weather stations are to be developed to assist with accurate forecasting of disease outbreaks and crop water use.

Plans are being developed to link growers, processors, researchers and PCMS through an easy to use computer network. Work continues on developing computer software that enables the provision of high quality services at the lowest cost possible.

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Other Publications from the project: The following publications relating to the PCMS project have been completed:

Developments in the U.S.A. Potato Industry. Report on a study tour to North West U.S.A. August 1993. M.A. Heap, Senior Horticultural Officer. (Copy submitted to H.R.D.C.)

The Provision of Potato Crop Management Services. Report on a study tour to North West U.S.A. August 1994. M.A. Heap, Senior Horticultural Officer. (Copy submitted to H.R.D.C.)

Potato Crop Management Service. Operating Manual. 1995/96 Primary Industries South Australia. Compiled by M.A. Heap & P. Frost. Edited by L Walters. Copy attached to Final Report.

Acknowledgments

This project was funded by the Horticultural Research & Development Corporation and McCain Foods, with growers contributing on a fee-for-service basis.

A special acknowledgment is due to Mark Heap, for his outstanding contribution to the development and provision of this service. Without Mark's creative mind, professionalism and tireless efforts, this project could not have evolved to deliver the high level of agronomic service that local growers were able to access.

On Behalf of Mark Heap and his team of collaborators, I would like to thank all potato growers who participated in this service for their input and vote of confidence in the service. A special thanks to Forrest Young, Tim Heysen and Graham Henman for their significant contributions as members of the Steering Committee.

This report was edited by:

B.G. Dowling, Horticulture Industry Development Officer PISA, Mt Gambier

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APPENDIX 1 PCMSREV.XLW

RESULTS - TABLE (NPV, IRR & BCR)

ALL COSTS EXISTING FUN INCLUDED TABLE EXCLU

Present Value of Costs $471,000 $160,000

Present Value of Benefits $9,556,000 $9,556,000

Net Present Value (NPV) $9,085,000 $9,396,000

Internal Rate of Return (IRR) 324% 939%

Benefit Cost Ratio (BCR) 20.29 :1 59.73

Annuity of Benefits $693,000 Annuity of Costs $34,000 Years of Project 24

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RESEARCH EVALUATION PROGRAM Chart 86

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Page 1

Report of a study tour to Oregon, Washington, Idaho and Wisconsin, U.S.A. - August 1993

M.A. Heap Senior Horticultural Officer, Primary Industries S.A., Mt. Gambier

CONTENTS Page

1.0 Introduction 3

2.0 Study tour objectives 3

3.0 Summary and recommendations 4

4.0 Seed handling and crop establishment 6 4.1 Seed diseases and suberisation 6 4.2 Seed piece size and plant distribution 7 4.3 Tissue culture 8

5.0 Plant nutrition 9 5.1 Nitrogen and groundwater 9 5.2 Sap nitrogen 10 5.3 Nitrogen strategies for commercial crops 11 5.4 Phosphorus 12 5.5 Potassium 13 5.6 Sulphur 13 5.7 Calcium 13 5.8 Trace elements 14

6.0 Irrigation 15 6.1 Soil moisture measurement 15 6.2 Irrigation scheduling for potatoes in the south east of South Australia 17 6.3 Current irrigation research and issues in the USA 17 6.4 Commercial irrigation practice in north west USA 18

7.0 Diseases and nematodes 19 7.1 Verticillium dahliae (Early die) 19 7.2 Colletotrichum atramentarium (Black dot) 20 7.3 Helminthosporum solani (Silver scurf) 21 7.4 Potato virus Y 21 7.5 Fusarium 22 7.6 Rhizoctonia solani (Black scurf) 22 7.7 Alternaria solani (Early blight) 22 7.8 Streptomyces scabies (common scab) 23 7.9 Nematodes 23

8.0 Insects 25 8.1 New systemic insecticides and transgenic potato cultivars 25

9.0 Weeds 27 9.1 Herbicides 27

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CONTENTS (Cont.) Page

10.0 Tuber disorders 28 10.1 Dark ends 28 10.2 Internal heat necrosis (IHN), internal brown spot (IBS), brown fleck 29 10.3 Bruise 30

11.0 Potato breeding/new cultivars 31 11.1 Transgenic cultivars 31 11.2 The North West potato breeding program 32 11.3 New french fry potato cultivars from the USA 33 11.4 Red fresh market potato cultivars from the USA 35

12.0 Storage 36

13.0 Processing 37

14.0 NASA and potato research 38

15.0 Consultants 39 15.1 Professional Agricultural Services 39

16.0 General notes 41 16.1 Russet Burbank, Shepody, Nooksack 41 16.2 Commercial practice 41 16.3 Agri Northwest - Colombia Basin 42

17.0 References collected on tour 45

18.0 Itinerary 49

19.0 Finance 50

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1.0 Introduction

Potato production in the south east of South Australia has risen from 35 000 tonnes in 1989 to more than 80 000 tonnes in 1993 and now represents half of the State's total production. This increase has largely been due to the construction of a french fry factory at Penola. The consumption of french fries in Australia has increased at about 6% per annum over the last 10 years and is increasing at exponential rates in neighbouring Asian countries.

Large areas of the south east of South Australia have the potential to produce quality tubers at a competitive price to supply future expansion of the french fry industry. The influx of new growers in non-traditional areas coupled with an increased demand for high quality Russet Burbank tubers has created a great demand for improved production technology. Pressure on growers to meet strict tuber quality parameters of french fry processing contracts is increasing.

The soils in proposed new areas are mainly coarse, infertile sands and problems related to water management and environmental stress have affected early attempts at potato production in these regions. New production technology must be introduced to realise the potential of the new areas. The USA is the largest producer of french fry potatoes in the world and is a clear leader in potato research. Several issues facing the expanding potato industry in the south east of South Australia are the focus of large research efforts in the USA, in particular the effect of environmental factors on tuber yield and quality.

The study tour was undertaken in two parts :

* The Conference of the Potato Association of America (a conference of scientific research)

* A study tour of university research facilities, processors, consultants and growers in the north west of the USA.

Acknowledgment

I am grateful to Safries (McCain Foods), Potato Growers of South East South Australia, Horticultural Management and Primary Industries S.A. for the financial assistance which made this study tour possible.

2.0 Study tour objectives

The study tour was planned to enhance the performance of existing and planned potato research and extension programs in the south east of South Australia, which include trust funded work on soil pH and potato growth, testing new potato varieties and research on the problems of water repellence and environmental stress for potato production on the vast areas of coarse sands in the south east of South Australia. The itinerary includes research leaders in soil and irrigation management, environmental stress, potato varieties and nutrition, as well as consultants to major growers and a visit to a large french fry processing plant.

An important objective of the study tour is to forge working relationships with leading research and extension people in major potato production areas of the USA to enable access to future advances. Ultimately, the study tour aims to improve the specialist knowledge available to the potato industry and increase its contribution to the South Australian economy.

3.0 Summary and Recommendations

Technology associated with potato production in the USA is, in most cases, well in advance of that found in Australia. This applies whether one refers to the status of research or to actual commercial practice. Apart from the obvious advantages that flow from the sheer size of the potato industry in the USA, there are several features of the research and commercial aspects of their potato industry which are worth considering :

- Potato research is often performed by large interdisciplinary teams, including plant pathology, entomology, nutrition, irrigation and general agronomy components. These individuals are sometimes located at a research centre (e.g. University of Idaho Research and Extension Centre, Aberdeen), however many advances are made by research teams with individuals located across states (as with the Tri-State Potato Variety Improvement scheme). Potato research involving teams of specialists should be encouraged in Australia. Co-operation between researchers across state and organisational boundaries may be guided by pressure from the Horticultural Research and Development Corporation for funded research to be of Australia wide significance.

- The large and diverse group of researchers working on potatoes and related fields in the USA is supplemented by university students. Many of these students are performing important research for the potato industry as post graduate theses. In addition, many university students are encouraged to spend vacation periods working as research assistants or as crop scouts. All of these exposures can only kindle understanding and enthusiasm among the next generation of scientists. I cannot recall a single exposure to the potato industry in my undergraduate years. The Australian potato industry would benefit by the encouragement/funding of post graduate research projects and a greater interaction with undergraduate students.

- Many regional research facilities in the USA combine strong extension efforts with traditional university research. US Department of Agriculture and state university personnel work closely together at these centres. The regional distribution of university researchers has resulted in significant practical research aiming to address the day to day problems of the local potato industry.

- The service industry surrounding the potato industry in Washington, Oregon and Idaho is excellent. In the Columbia Basin (Washington) the use of fee for service consultants is common, few growers take it upon themselves to make all fertiliser, pest and disease and irrigation decisions alone. Most growers realise that keeping up with, and applying, all of the latest technology and running a large agricultural business is now not a practical option. In addition, margins are slim and "educated guess" mistakes cannot be absorbed. In general, a manager of a potato enterprise in Washington scientifically measures and adjusts many aspects of crop growth weekly - by neutron probe, soil sampling, petiole sampling and infra red photography. I feel this is the major difference between the Australian potato grower and his counterpart in the USA. In fairness, most potato growers in Australia do not have access to these services.

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Many technical issues were examined on the study tour and are presented in this report. Issues worth highlighting are :

- Early dying of potatoes, particularly Russet Burbank, is a major research concern throughout the USA. Yield losses of 15 - 30% are often reported in the absence of control of the Vierft'«7/ium/nematode complex. Symptoms resembling those reported for early dying are common in Australian potato crops, but little work has been done to examine the causes here. It is possible that potato crops grown in many areas of Australia are debilitated by a complex of PVYIColletotrichumlVerticillium.

- Phosphorus nutrition of the Russet Burbank variety is a key factor in the production •.-•£' high yields of quality tubers in the USA. Some researchers in the USA were concerned at the low levels of phosphorus recorded in Russet Burbank crops in south eastern Australia. These low levels could be related to several factors, including Verticillium early die.

- Environmental concerns are impacting strongly on potato research programs and commercial practice throughout the USA. This is particularly evident for nitrogen fertiliser strategies (ground water contamination fears) and for the chemical control of early blight.

The large number of serious potato pests and diseases encountered in the USA which are not ye; known in Australia should remind all of the importance of plant quarantine regulations.

The french fry cultivar development program operating in north west USA is very impressive, showing the benefits of co-operation between teams of skilled researchers in the three states. The Australian french fry potato industry should continue its relationship with this program. In particular, the french fry industry of south east South Australia should take note of trials of new french fry cultivars from this program in Texas and Nebraska, where growing conditions and soils are similar to ours.

The production of transgenic potato cultivars is a rapidly expanding area. The Australian potato industry should carefully consider the emerging trend toward the development and ownership of these new cultivars by large private companies.

The diversity and standard of research papers presented at the PAA Conference at Madison (Wisconsin) proved beyond doubt to me that, despite recent cutbacks, the technology surrounding the potato industry in the USA will continue to set high standards. Researchers and others associated with the Australian potato industry should be encouraged to interact with their counterparts in the USA; we have all to gain and nothing to lose.

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4.0 Seed handling and crop establishment

Seed handling and potato crop establishment continues to receive a large input from research and extension in the USA. Research and extension personnel have combined to promote the practical aspects of achieving evenly spaced stands of vigorous plants and have made a large impact on the performance of growers in north west USA. Dr. Robert Thornton said that the major change in productivity for Russet Burbank in north west USA in recent years has been plant population (uniformity of placement and population) and seed piece vigour (health, size etc.).

Current research programs focussing on the suberisation mechanism and diseases associated with cut seed is of great relevance to Australian potato growers.

Valuable sources of information on seed handling and crop establishment were:

- Dr. Gale Kleinkopf (University of Idaho Research and Extension Centre, Kimberley, Idaho) - Dr. Robert Thornton (Washington State University, Pullman, Washington) - Mr. Steve Holland (Crop consultant, Othello, Washington)

4.1 Seed diseases and suberisation

Several research programs are in progress to examine suberisation and resistance mechanisms to disease organisms of seed tubers. Dr. Edward Lulai (PAA Conference paper) estimated that $200m/year is lost in the USA due to damage to seed tubers. Recent work has examined the time taken for the formation of the suberin layers (phenolic and aliphatic components) which join to form a physical barrier to infection. The phenolic (outer) layer is related to soft rot resistance, whilst the aliphatic (inner) layer is responsible for Fusarium (dry rot) protection. The time taken for the completion of these protective layers varies between potato cultivars, but is generally 2-3 days for the phenolic components and 5-7 days for the aliphatic components.

Dr Wayne Jones (Idaho Falls, University of Idaho), working on seed diseases and suberisation, has found that some seed treatments not only affect causal organisms, but may also slow or speed up the rate of suberisation. The product Maxim® (Ciba Geigy) has performed well against Fusarium diseases of cut seed.

Dr Walt Stevenson (Madison, University of Wisconsin) is part of a team evaluating options for improved management of potato diseases which is developing an expert computer system for predicting seed losses at planting. Dr. Stevenson stressed that although this computer program takes into account an enormous number of factors that affect seed piece loss, suitable conditions for suberisation of cut seed remains the critical issue.

Dr. Robert Thornton and Mr. Steven Holland (consultant to the potato industry in the Columbia Basin) are investigating the effect of seed piece bruising on suberisation and subsequent seed piece losses. Bruised tissue doesn't suberise, leading to invasion by decay organisms. In last year's research, where seed pieces were cut by hand and bruised, 75% of bruises subsequently showed decay. This year it was 90%. The work is also comparing sharp and blunt cutting knives. A dull knife leads to 10% more of the cut surface suffering decay than with a sharp knife due to the failure of torn/damaged tissue to produce suberin. For pre-cut bruising (i.e. damage at seed tuber harvest), poor suberisation and decay results if the cut goes through the bruised tissue.

For commercial seed it has been noted that there are 8 bruises (on average) on the cut surfaces of a seed piece. Bruises come from the cutter (drops), barrel dusters, loading seed over the side of

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trucks and in the planter.

The resistance of Fusarium to seed treatment chemicals is now common in the USA. Pre-cutting of seed, commonly 12 days - 1 month in advance of planting, is one of the factors thought to contribute to the problem. Columbia Basin potato growers prefer to plant out seed within 36h of cutting into moist soil.

4.2 Seed piece size and plant distribution

Growers in the USA have traditionally said that the weight of seed planted per acre was the key issue, and have only recently examined seed piece size x planting arrangement in detail. Total yield and tuber size are dependent on seed piece size and planting arrangement and Dr. Thornton says that close attention to these aspects have gained commercial growers in the Columbia Basin 5-7 t/ha.

A wide range of opinion exists over the ideal seed piece weight. Dr. Gale Kleinkopf has found that, for Russet Burbank, seed pieces less than 40g (about IViozs) should be discarded. This contrasts strongly with existing practice in south east South Australia where discarded 'slivers' are generally up to 15-20g. Planting small pieces (20-40g) not only decreases total yield, but also increases the proportion of small tubers at harvest. Dr. Kleinkopf has found that there is a yield response up to 112g (4oz) seed piece size for Russet Burbank, but an 84g (3oz) seed piece is where the extra cost of seed is not compensated for by extra yield. Pieces between 84-112g (3-4oz) are too large for standard cups and should not be re-cut (each half is too small).

Dr. Kleinkopf has found a straight line relationship between seed piece size and stems produced for any seed lot of Russet Burbank. Stems per metre of row is a better measurement of potato population than plants per hectare. Seed producing about 4 stems per piece (56g/2oz piece) is about the right physiological age for Russet Burbank. Less than 3 and more than 7 stems leads to a decline in saleable tubers. Determinant varieties (often earlier types) such as Shepody are not affected by stem number as much as Russet Burbank. The rationale for more stems (or plants) per area in Shepody is driven more by individual tuber size and shape than actual yield. Knocking sprouts off seed pieces that are physiologically old does more harm than doing the same to young seed.

Dr. Kleinkopf is currently looking at seed storage conditions and seed performance, with special attention to temperature oscillation in storage. Current recommendation for seed storage is 3-4°C but temperature fluctuations can be as great as 2-6°C. Humidity control is desirable but not available in many Idaho seed stores.

Dr. Thornton said that the current commercial recommendation for Russet Burbank seed piece weight is around 56 g (2.0ozs). He feels that 50g (1.75ozs) is acceptable if the cutter is producing a narrow distribution of seed piece sizes. It is a common practice in the USA to draw distribution curves of seed piece weight from the cutter. The average seed piece size may be easily changed by shifting the position of the distribution curve, however it is important to also control the shape of the curve to a narrow range.

Drs. Thornton, Kleinkopf and Jones all indicated that efforts to improve the even spatial arrangement of plants in the row show a greater return than the 'often seen' fine tuning of the average distance between plants in a row.

Plant population is important for reasons other than yield. A vigorous evenly spaced stand of

T /

Russet Burbank leads to early canopy closure and lower soil temperature, leading to a reduction in stress related disorders of the tuber, and improved tuber shape and size.

Mr. Holland works closely with Dr. Thornton with commercial growers in the Columbia Basin and has concentrated on the practical aspects of improving the spatial arrangement of potato plants. His specialty is the fine tuning of seed cutting and planting machinery. In their program a "correctly placed seed piece" is within ±_ 10% of the desired spacing. They found that the average performance for growers before adjustment was 45% of pieces correctly spaced. In the last 3 years of the program this has leapt to more than 80% for participating growers. To achieve this result the seed profile should contain at least 70% of pieces between 40g and 84g (IVi and 3oz). Grading rollers set 18mm (%") apart are used to take out the smalls. A commonly corrected fault with seed cutting machines in the region is overloading the front of the cutter, which causes whole tubers to bump on the line feeding the machine, causing poor alignment. Chip rollers (small piece removers) are also often overloaded, allowing smalls through. The best uniform shape comes from seed tubers less than 250g (9oz). These pieces will have a uniform roll. Bigger seed tubers will result in a greater range of piece shapes. If there are more than 50% of pieces with 2 or more cut surfaces at right angles, there will be problems at planting. Pieces > 98g (3'/2 oz) are re-cut by hand.

Planter speed is generally best between 4km/h and 4.5km/h (2.4 and 2.7 mph). Fine tuning is done at 0.06km/h (l/10mph) increments. Fine tuning must be done for each seed batch (or cutting setting). There must be an accurate measure of ground speed. Ground speed radar is used by 90% of growers in the Othello (Washington) area, costing between SUS600 - $2,000. The best systems are connected directly to the tractor throttle, instantly compensating for wheel slip or other factors.

Planter bowl depth is kept to a minimum (before skips start). Often this is about 5 - 7 kg of seed for US planters. To test this, the supply to the bowl is blocked and the level at which skips start is noted.

4.3 Tissue Culture

Several large, privately run tissue culture laboratories now supply mini-tubers and plantlets to the seed industry. One of these is Summit Plant Laboratories in Fort Collins, Colorado. Prices in 1993 were; minitubers 3-10g, 55C US each, large minitubers (> lOg) $27US/450g (lib), in-vitro plantlets 450 US each. The demand on tissue culture material is increasing as earlier generation material is used for commercial production. Generation 7 (GO = minituber, Gl = first year in the field) tubers are now rare, generation 5 is now considered "old seed" and the trend is toward generation 4.

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5.0 Nutrition

As in Australia, a large research effort into plant nutrition for potatoes continues in the USA. Importantly, however, the emphasis of the research has changed in recent years and is now more concerned with the interaction of plant nutrition with a wide range of issues other than the traditional work relating nutrition to tuber yield and quality. Plant nutritionalists in the USA are often involved in large multi-disciplinary teams which conduct research programs including the effect of plant nutrition on pests, diseases and the whole farming system in which potatoes are part.

Valuable sources of information on potato nutrition were:

- Dr. Gale Kleinkopf (University of Idaho Research and Extension Centre, Kimberley, Idaho) - Dr. Robert Thornton (Washington State University, Pullman, Washington) - Dr. Al Mosely (Oregon State University, Corvallis, Oregon) - Dr. Jeff Stark (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Dale Westermann (University of Idaho Research and Extension Centre, Kimberley, Idaho) - Dr. Keith Keller (University of Wisconsin, Madison, Wisconsin) - Dr. Clint Shock (Malheur Experiment Station, Oregon State University, Ontario, Oregon) - Mr. Robert Thornton (jnr.) (Agri-Northwest, Pascoe, Washington) - Dr. Bill Dean (Irrigated Agriculture Research and Extension Centre, Washington State

University, Prosser, Washington State)

5.1 Nitrogen and groundwater

Nitrate contamination of groundwater is a critical issue for the potato industry in the USA. Several multi-discipline teams are working the measurement of nitrate leaching from potato crops and on approaches to reducing nitrate leaching.

A team of three Phd students directed by Dr. A. Mosely (University of Oregon) is working on nitrate contamination of ground water by potatoes grown in the Hermiston - Columbia Basin area (a declared groundwater zone). Mr. Jeff Mc Morran is measuring nitrate leaching from the potato cropping system. Mr. Sydney Fernando superimposes rotational crops after Mr. McMorran's plots of potato looking at deep rooted crops to capture nitrate that has gone past the potato root zone. A third student is working on root zone growth for cropped plants.

A publication outlining previous work on nitrate contamination of groundwater in the Columbia Basin is "Research for Reduction of Nitrate Leaching into Colombia Basin Groundwater" by Max Hammond (Oct 1992). This study examined many soil irrigation factors using a grid-sampling approach.

Nitrate leaching is now a major concern of the Integrated Potato Crop Management team working from the Hancock Research Station in Wisconsin. The team approach has significantly reduced, but not eliminated, nitrate contamination of groundwater by potato crops. The specialists in the team (about 10 researchers) have all had to consider the issue since nitrogen management not only influences tuber yield and quality but also pest and disease incidence. In particular, reduced nitrogen regimes aiming to minimise nitrate contamination of groundwater, have been found to increase Colorado beetle feeding and problems with early blight.

Several complementary areas of work are also in progress to assist the management of nitrate leaching from potato cropping systems. Dr. Jeff Stark is examining nitrogen cycling in irrigated

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legume - potato cropping sequences. The research has recorded nitrogen mineralisation patterns, nitrogen uptake patterns (in potato), potato yield and quality, and residual N. This work has great significance for potato crops in Australia.

In one experiment on a sandy loam soil type, the release rates of nitrate from different types of crop residue were recorded by Dr. Stark . The main plots were alfalfa, peas, oats and peas/oats. Russet Burbank potatoes were grown in rotation with these crops with subplots of ammonium nitrate applied at 0, 45, 90 and 180 kg N/Ha. Graphs of N-mineralisation (nitrate - N) vs. time for main plots (alfalfa, peas, oats and peas/oats) showed a steady increase for ploughed in residue over 225 days, although the rate of increase of soil nitrate - N slowed after 100 days (except pea/oat, where a delay in mineralisation was recorded). The main plots (crops) influenced the timing and total amount of N available and will be used in designing nitrogen strategies for future potato crops. This information must be calculated for potato cropping systems in Australia.

Nitrogen strategies interact strongly with irrigation practice; Dr Dale Westermann has found that 25 mm (1") of water on sand or silt loam is enough to leach out most of the available nitrate from the root zone. Potato root zones are shallow in Idaho; they are limited to about 30 cm (12") in many places by a CaC03/Silicon layer. This layer prevents root growth but not water movement. Dr. Westermann says that petiole nitrate-N should be less than 10,000ppm 30 days before harvest for Russet Burbank. Nitrate levels may exceed this in potato crops in south east South Australia due to heavy applications of nitrogen in combination with unknown amounts of nitrogen released by mineralisation of pasture residues.

5.2 Sap nitrogen

Several research programs are examining techniques for the rapid determination of the sap-nitrogen status of potato plants. Dr. Mohamed Errebhi, Dr. George Silva and Dr. Leigh Morrow each contributed papers on these techniques to the PAA Conference. These research programs aimed to evaluate Horiba and Hach electrodes as an aid to rationalising nitrogen use. Relationships were determined between sap N and dry weight N. These readings were calibrated to potato performance.

The Horiba Cardy meter for measuring sap nitrate levels is gaining acceptance in Australia. Dr. Errebhi presented the following calibration data for nitrogen levels measured by the Horiba for Russet Burbank potatoes (4-5th petiole, leaflets stripped, used to obtain sap):

Published adequate range- Crop Stage Horiba Sap dry petiole nitrate - N

22,000-17,000 Early 1650-1300 15,000 - 11,000 mid 1200 - 900 8,000 - 6,000 Late 700 - 550

All three researchers found the Horiba and Hach to be adequate for assessing sap nitrate - N, but a large number of perceived problems were raised from the floor during discussions at the PAA Conference. One view is that these approaches to measuring sap nitrate are also "a good measure of plant moisture status", i.e. nitrate levels measured in the sap vary greatly with crop moisture status. I have formed an opinion that, with rapid turn-around times, dry petiole analysis (which also include other elements) is the best approach for nitrogen management in commercial crops

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5.3 Nitrogen strategies for commercial crops

Dr. Stark uses a three way table to design nitrogen strategies for potato crops:

1. Soil nitrate - N tests

2. Ploughed in residue (previous crop). Calibrated knowledge of nitrification of the crop is needed.

3. Yield potential of the crop.

This strategy is then modified for the growing crop by a combination of soil and dry petiole analysis. Soil sampling for nitrogen is done weekly by some growers in the Columbia Basin and is used in combination with petiole testing. Nitrate-N soil tests are performed by Ca2Cl extraction. Soil nitrate testing in the laboratories serving crop consultants use Specific Ion Electrodes, e.g. Orion or Hach. A known weight of dry soil (e.g. lOg) is put in a flask with KC1 solution and swirled for 30 minutes. This is filtered and then analysed by SIE.

Other methods are available, including the spectrophotometer (in conjunction with solicyllic acid).

Several researchers felt that petiole nitrate-N results are "useless" by themselves and should be examined along with soil nitrogen data. In their view petiole results are a "snapshot of the past" which is only useful for predictive purposes when combined with a measure of available nitrogen in the rootzone. Dr Bill Dean has found that petiole nutrient analyses are often not well correlated to yields and feels that soil nitrate levels are better for making future fertiliser decisions. The shape of petiole nutrient curves is, however, very useful for retrospective analysis of a nutrition strategy. Dr. Dean said that in general the minor elements were not used in soil tests for growing crops (except zinc). Soil tests during growth are mainly looking at nitrates and ammonia. Soil samples for potatoes should be at taken to at least 30 cm (12"), and are often taken to 45 cm (18"). These samples are not normally stratified. In Australia soil tests for potatoes are rarely taken after planting, and then only taken to 20 cm.

Dr. Stark said that petiole samples for nutrients should be taken randomly over the total area to be represented. Several samplings, close together in time are best; this gives a better idea of trends (shape of nutrition curve). It also helps to identify "faulty readings". Several crop consultants use an approach where petioles are taken from the same narrow strip within the crop at each sampling occasion. This is perhaps expediency - the collection of petioles takes less time.

Most commercial crops in the USA pre-plant broadcast most of the basal fertiliser but also band some fertiliser as well. The method of applying planting fertiliser is confused in south eastern Australia. Many growers band all or broadcast all fertiliser, often in line with machinery limitations. I am now convinced that the combination of broadcasting and banding is the best for sands and loamy sands, where the low buffering capacity of the soil can lead to crop establishment problems if high rates of fertiliser are banded. Dr. Dean prefers the "limited broadcast" method of applying pre-plant fertiliser. With this method, fertiliser is dropped in strips before planting on pre-marked planting rows. This reduces the amount of waste associated with normal broadcasting methods.

For calculating fertiliser programs, the efficiency of nitrogen use for broadcast pre-plant fertiliser is estimated at about 50% and the efficiency of ammonia, urea and nitrate applied through irrigation water is estimated at 75 %.

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Recommended nitrogen strategies vary greatly between and within varieties. One area of continuing conflict is the issue of "spoon-feeding" versus "up-front" nitrogen fertiliser for Russet Burbank potatoes. Dr. Keith Keller is an advocate of applying a large proportion of applied nitrogen before the hook stage, even on sandy soils. Dr. Stark, and many others, advocate the continual (but tapered) addition of nitrogen throughout Russet Burbank crop growth. Dr Stark has found that excess nitrogen early can cost 2-3 weeks delay in tuber bulking in Russet Burbank.

Dr. Clint Shock has found little difference in nitrate-N measured in petioles from Russet Burbank and Shepody grown with the same fertiliser program. However, he has examined industry claims that nitrogen is best applied up-front (planting) for Shepody rather than side-dressed (on silt loam), and agrees. Dr. Shock says that less nitrogen should be applied to Frontier Russet than Russet Burbank.

Mr. R. Thornton Jnr. grows 400 ha (1 000 acres) of the Nooksack cultivar, a variety suited to the harsh conditions on the coarse sands of south east South Australia. Mr. Thornton stressed the importance of low applications of nitrogen before tuber set for this cultivar - a moderate amount of nitrogen should then be applied through the tuber bulking stage.

5.4 Phosphorus

Observation of phosphorus levels in Russet Burbank potatoes in the south east of South Australia have often found a rapid decline from around 0.4% in dry petiole samples at the 50mm king tuber stage to 0.2 or less only 2 weeks later. This situation is of great concern and researchers in the USA were asked to consider the situation.

Dr. Westermann said that once P levels in dry petioles fall below 0.2% for Russet Burbank plants there is a great increase in Verticillium activity. Verticillium is an opportunist that preys on weak plants. Low P levels are also noted in late growth in Russet Burbank in Idaho when plant roots are debilitated by Rhizoctonia and nematodes. P levels must be kept well above 0.2%, preferably over 0.3%, until 30 days before harvest. P is taken up mainly by new roots in potatoes, low P leads to poor new root growth - a circular worsening of the problem. Dr. Jim Davis (Aberdeen Research Station, University of Idaho) has also found a strong relationship between low P levels and early dying disease caused by Verticillium.

Foliar sprays cannot safely put on enough P to solve serious deficiencies. 10-34-0 (ammonium poly phosphate - neutral pH) is often applied through centre pivots when P problems are anticipated in north west USA. 20-40 kg of P2Os /ha (10-20 kg of P) are put on per application. For 10-34-0 to be effective conditions must be cool, the soil moist and full canopy closure to encourage root growth in the top 2 - 5 cm of the soil. If 10-34-0 is used in alkaline water, precipitation may result, blocking nozzles. Dr. Westermann noted that although the old school said P was useless applied through water, good results are coming from this approach which is now common in the Columbia Basin.

Growers in Idaho pre-mark the paddock and deep shank some phosphorus fertiliser before planting. The initial roots formed by emerging potato plants are above the seed piece and some phosphorus is also placed above the seed piece. In high aluminium soils, some phosphorus may precipitate as Al-phosphate. Dr. Westermann said Kennebec has a high ability to take up P (one of the best), while Russet Burbank by contrast is a poor scavenger of P. It is possible that poor Russet Burbank root development in some areas is related to low P in the plant. Under low soil pH and high Aluminium, the effectiveness of broadcast P is reduced. Work should examine how much P is available in the second strata (15 to 30 cm) in potato soils in south eastern Australia.

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Dr Stark felt another possible explanation of rapidly declining P levels in Russet Burbank in the south east of South Australia may be a dilution effect from rapid vine growth, resulting in turn from heavy applications of water and nitrogen at a period of high temperature.

5.5 Potassium

Idaho silts and sandy loams have good natural levels of potassium but have been mined by cropping and levels are getting lower. Dr. Westermann is looking at the post plant application • f K; different sources of K now available and the application of K through the irrigation system. Sources of K available include: Muriate, K thiosulphate (KTS), and a new granular potassium sulphate.

Dr. Westermann has found that muriate of potash can depress tuber specific gravity, but this a complex picture. This is not a simple chloride ion problem, but is also related to the level of nitrogen and the different solubility of K in muriate versus sulphate. Although high chloride levels depress nitrate in the plant, the measured level of proteins is not affected and plant growth should not be impaired. The thiosulphate form of K was best for specific gravity of tubers in trials last year. If K is applied at recommended rates, the muriate form of K gave a similar specific gravity as sulphate K. If heavy rates are applied, K-sulphate is better than muriate for high specific gravity.

Commercial growers and their consultants in Washington State and Idaho often said that planting fertiliser may include muriate of potash but they will only apply the sulphate form of potassium at sidedressing.

5.6 Sulphur

Low sulphur levels are often of concern in potato crops grown on acid sandy soils in south eastern Australia. The critical level proposed for sulphur in dry petioles from Russet Burbank potatoes varies greatly throughout the USA. Part of the reason for this may be the poor repeatability of laboratory tests for sulphur in petioles and soil. Sulphur levels in dry petiole analysis thought to be critical at early tuber bulking ranged from 0.20% to 0.35%.

Dr. Westermann said that tuber growth is retarded by low Sulphur levels, but warned that if this situation is remedied during the tuber bulking period, tuber quality problems often result with resumed growth.

5.7 Calcium

Several research programs are examining calcium and potatoes in the USA. This is mainly because low calcium level in the tuber is implicated in many tuber physiological disorders, such as soft rot and internal brown spot (see 10.2 - tuber disorders).

Dr. Ahmed Tamfik reported research (PAA Conference) examining the effect of adding calcium to potato crops during tuber bulking. He found that tubers are almost always deficient in calcium, even when the potato vine had sufficient for healthy growth. This can be explained by the mechanisms of calcium uptake and transport. Tubers may only take in calcium by the small roots coming from the tubers and stolons, the calcium taken up by the main root system remains in the vine. The vine may remove calcium from the tuber at times of rapid growth, whilst calcium is not translocated to the tuber.

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Dr. Tamfik added calcium to Russet Burbank potatoes in a "spoon-feeding" manner during tuber bulking, with treatments adding 113 or 226 Kg/Ha of calcium nitrate. Calcium nitrate had nil effect on tuber calcium in some years, slight in others. Many other researchers have found inconsistent effects of adding calcium. Calcium applied by overhead irrigation has been found to give the best results.

5.8 Trace elements

Little research activity was evident in the USA on trace elements and potatoes. In addition, commercial growers and crop consultants showed only a routine interest in trace elements - trace elements are measured in regular petiole testing of crops and adjustments made with foliar sprays when necessary. Growers and consultants appeared to be satisfied that existing data for the interpretation of trace element levels in petiole samples were satisfactory and did not question them. I found this of interest - given the large disparities in critical levels in common use for most trace elements.

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6.0 Irrigation

Irrigation research on potatoes in the USA is often conducted as part of a team effort examining the interaction of irrigation, nutrition and pests and diseases on cropping systems. Particularly important issues facing irrigation researchers are pollution of underground water supplies and the efficient use of dwindling water supplies. The availability of water for horticulture varies greatly in the USA, with supplies becoming critical in some south western states. The accurate and reliable measurement of soil moisture in potato crops is an important issue for this research, and for the irrigation management of commercial crops. Neutron probes have served the potato industry reasonably well, and are still the favoured tool of commercial crop consultants, however, most researchers are aware of the limitations of the probe in the potato cropping system.

Dr. Clint Shock (Malheur Experiment Station, Oregon State University, Ontario, Oregon) has invested a large effort in examining new devices for the measurement of soil moisture as an aid to work on the irrigation of potatoes. Dr. Shock was particularly helpful in addressing the practical problems faced by potato growers in the south east of South Australia. Other valuable sources of information on irrigation and potatoes are:

- Dr. Jeff Stark (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Mr. Jeff McMorran (Hermiston Agricultural Research and Extension Centre, Oregon State

University, Hermiston, Oregon) - Dr. James Lorenzen (North Dakota State University, Fargo, North Dakota) - Mr. Michael Stevenson (Professional Agricultural Services, Pascoe, Washington State) - Dr. Steven Rawlins (Irrigated Agriculture Research and Extension Centre, Washington State

University, Prosser, Washington State) - Dr. Gale Kleinkopf (University of Idaho Research and Extension Centre, Kimberley, Idaho).

6.1 Soil moisture measurement

Dr. Shock has a large lysimeter set up in a phytotron for examining new devices for measuring soil moisture. In these comparisons, up to 24 replicates of the device are set up in the lysimeter and their readout logged on computers to be compared with gravimetric measurements and with other devices (such as tensiometers). Dr. Shock has examined a range of soil moisture measurement equipment including:

Time domain refiectometry devices Temperature devices Di-electric devices Neutron probe

Dr. Shock does not favour the neutron probe for potato irrigation management:

Poor ability to measure water in the important upper root zone May measure wet "untapped soil" just below the root zone It measures water in tubers It measures differently if your foot is above the probe Physically visiting the site for each measurement causes compaction and alters the readings

Some of the above are not as important in Washington State where root systems are deep in the loamy sand. Russet Burbank root systems in Idaho are shallow in the silt loam soil. In the South East (where clay may be at 30 - 45 cm) the neutron probe "ball" may record a lot of "useless

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water".

A device tested over the last three years by Dr. Shock is the Granular Matrix Sensor (GMS). This has shown great promise as a simple, inexpensive system which can be logged. Several research papers have been submitted for publication on the performance of the device in potato crops, including papers on calibration of GMS for irrigation management and the placement of the sensors in and under the potato ridge. Papers examining potato irrigation in general have recently been submitted for publication which use the GMS device to record soil moisture in the research. The sensor ("200 x") and digital hand held reading device ("30 KTC") are available in Australia from the Irrometer Company under the trade name of "Watermark". Computer logging is also available for the sensors from Irrometer and also from Australian companies. The probes cost around $US 20, the hand held meter around SUS 150 and the logger around $US 1 500. Dr. Shock uses a radio transmitter to relay information from a logger in field plots to his laboratory. Unfortunately, the transfer of signal from the sensors to the logger is by cables.

The sensor consists of a granular medium encased in a steel tube with membrane windows to allow the passage of moisture between the matrix and the soil. The hand held reading device simply converts the changing electrical resistance of the wetting/drying granular medium and converts this to centibars of suction. The sensors should be tested carefully in each soil type, since it is possible that the GMS membranes may have similar contact problems with coarse sands as experienced by the traditional tensiometer.

Variation in paddocks means that many sites may be needed to schedule irrigation. A compromise is to pick a "typical site" (or sites) and a "dry site". The dry sites result in tuber quality defects (such as dark ends) if not managed properly and can contaminate the tuber sample at harvest. Swamps or areas with poor drainage should not be allowed to influence irrigation decisions for the rest of the crop - write these areas off if necessary. A typical commercial crop monitoring set up using GMS for one field is 4 shallow sensors (see publication on the location of sensors in the potato ridge) at "average sites", 4 shallow sensors at "dry sites", and 2-4 deep sensors. A basic GMS set up with logger can handle up to 12 probes and a temperature probe (to modify the curve).

Commercial potato crop consultants in the USA mainly use the neutron probe for scheduling irrigation. Despite the perceived problems of the probe for scheduling irrigation in potatoes, the consultants and their clients seem well satisfied with the field performance of the probe; especially in the deep loamy sands of the Columbia Basin. The neutron probe system allows for the investment in capital equipment to be spread over many potato crops (as the device is carted from site to site). Logging systems, such as the GMS, entail a substantial capital investment for each crop monitored. Despite this, I feel that a logging system is worth paying for in the south east of South Australia where potatoes are often grown in coarse sands and the effect of each irrigation is transitory. Weekly visits with a neutron probe are not well suited to this situation.

Many potato crop managers in the USA use the well developed satellite system for meteorological information to assist with irrigation decisions. The satellite system uses a grid of computerised ground stations which transmit a range of meteorological information to the satellite every 15 minutes. A very important component of this is evapo-transpiration (Et) data. This allows the use of Et x crop factor to check on irrigation decisions or, in some cases, to actually schedule the irrigation of crops.

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6.2 Irrigation scheduling for potatoes in the south east of South Australia

Discussions were held with several researchers in the USA concerning a practical approach to scheduling irrigation for potato crops in the south east of South Australia. Several problems exist in this region which confound the scheduling of irrigation simply by readings from soil moisture measuring probes - the major issue being the extreme variability of our soils, with large changes in water repellence, depth to clay and organic carbon over short distances. The new generation of soil moisture measuring devices are accurate - but only measure soil moisture at the point at which they are inserted. A large number of sites must be carefully chosen within the potato crop to overcome this variation.

Evaporation multiplied by crop factor is used to schedule irrigation for many potato crops in the USA. This method is known to work well over a range of soil types and was suggested by Drs. Shock and Stark as a good starting point for growers in the south east of South Australia for scheduling irrigation of potato crops. In this situation, the soil measuring devices would be most useful as an aid to check or modify irrigation scheduled by evaporation and crop factor. Crop factors are available for several potato cultivars, having been calculated on many occasions in the USA and Australia. To determine the "trigger point" for the commencement of irrigation, the readily available water (RAW) in the rootzone of the plant must also be known in addition to the % depletion of RAW before stress commences. Dr Shock was unhappy with the common "blind quotation" of 50-60% of RAW depletion as the trigger point for irrigation - it changes between soils and crops. An accurate soil depletion curve is needed for each soil type.

The progress of this strategy should also be checked by soil samples for gravimetric determination of soil moisture at 0-30 cm and 30-60 cm, and by examination of crop health.

It is now possible to get evaporation readings to directly run the irrigation system. The Atmometer (a porcelain cup that loses water analogous to crop use) is used for this purpose. The Atmometer costs about $US 80 - 100 for the basic device. With a logger and irrigation control this exceeds $US 1,500.

6.3 Current irrigation research and issues in the USA

Nitrate contamination of groundwater is a serious concern in many parts of the USA. One researcher put the situation in this way: "Up to now some big growers (in the Colombia Basin especially) haven't got sophisticated about irrigation management; they have overwatered without bad consequences. Now the nitrate issue will force better irrigation management." Current research is looking at different irrigation strategies vs. nitrate leaching.

Dr. Shock and others are examining the effect on tuber yield and quality of reduced irrigation applications at different growth stages. This work aims to identify those periods of potato growth where less water can be applied without severe yield and quality effects. In addition, new lines in the variety improvement scheme are being examined, looking for potato varieties that don't crash in yield or quality with small variations in water stress - such as is the case for Russet Burbank. Nitrate leaching is measured by deep core sampling of the soil (6 feet) in each plot before planting and after harvest. The current irrigation aim is to keep the top one foot of soil uniformly wet without loading up the second foot.

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6.4 Commercial irrigation practice in north west USA

Several crop consultants offer irrigation scheduling services to potato growers in the Columbia Basin area. The use of these consultants is the normal practice - one consulting company schedules irrigation for more than 7,000 ha (18,000 acres) of potatoes around Pascoe (Columbia Basin). These services mainly use neutron probes in conjunction with infra-red photographic techniques. Evapotranspiration and crop factor is also a tool employed to check on irrigation requirements. One irrigation crop consultant in the Columbia Basin uses the following guide (crop factor) for Russet Burbank potatoes at tuber bulking (peak water use):

crop factor (% class A)

100% in sand 95% in loamy sand 90% in sandy loam 88% in silt loam

To assist with irrigation scheduling, an irrigation forecast program can be bought from Washington State University, called WIF (Washington Irrigation Forecaster). This is fed with up­dates on conditions from satellite, which receives data from weather stations every 15 minutes.

The crop factor/Et approach relies on accurate assessment of crop stage (irrigation requirements are related to canopy cover). Dr. D. Curwen (University of Wisconsin) is trying to use P-days (used in the early blight program) to stage crop development for irrigation programming.

A common belief amongst farmers in north west USA is that there is no advantage in night irrigation. In fact, most perceive quality benefits from overhead irrigation during the day. A typical Columbia Basin Russet Burbank crop is irrigated with 650 - 750 mm of water. The water is of very high quality, coming from melted snow.

Many growers had articulated (corner system) pivots, designed to use more of square fields. These pivots are known as "a pain in the neck" and are generally thought to be not worth the effort. Among the many problems; the pressure is distorted as the articulated arm turns on and off and mechanical failure is common. Although potato enterprises in the Columbia Basin are very large, most centre pivots were around 50 - 55 ha (120 - 140 acres). I feel that the lessons concerning very large centre pivots (say 80 ha) and potatoes has yet to be fully appreciated in some areas of Australia.

An interesting concept being developed by Dr. Stark and others is computer controlled centre pivot systems. This allows the differential management of water to allow for soil and other variations under a centre pivot.

1. Grid sample the paddock - topography, swamps etc, water repellence, depth to clay, infiltration notes.

2. Produce a computer map of paddock grid. The computer is linked to the centre pivot arm and follows its position.

3. Emitters on the centre pivot have solenoid control, allowing on/off or intermittent activity.

The set-up is checked by thermal infra red video taken at 1,500 m for fine tuning and will soon be available commercially. The potato growing soils of the south east of South Australia are extremely variable and would benefit from this concept.

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7.0 Diseases and nematodes

Several plant pathologists are specialists on potato diseases in the USA. The number and quality of papers on potato diseases at the PAA Conference was outstanding. Fusarium infection of potato seed tubers, early dying syndrome caused by Verticillium dahliae/nematodes, black dot disease caused by Colletotrichum atramentarium and target spot (Alternaria solani) are areas of strong research activity. The approach to dealing with serious diseases of potatoes has changed rapidly, with many programs examining the use of antagonistic organisms and the rapid introduction of resistance genes from wild solanums through transgenic technology. Significant findings have emerged concerning the interactions of pathogens; many diseases pre-dispose potato plants to further invasion.

Valuable sources of information on diseases of potatoes were :

- Dr. Jim Davis (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Dennis Corsini (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Dennis Johnson (Irrigated Agriculture Research and Extension Centre, Washington State

University, Prosser, Washington State) - Dr. Doug Rouse (University of Wisconsin, Department of Plant Pathology, Madison, Wisconsin) - Dr. Mary Powellson (Oregon State University, Corvallis, Oregon) - Dr. Hassan Mojtahedi (Irrigated Agriculture Research and Extension Centre, Washington State

University, Prosser, Washington State) - Dr. Jerry Santo (Irrigated Agriculture Research and Extension Centre, Washington State

University, Prosser, Washington State) - Dr. Wayne Jones (University of Idaho, Idaho Falls, Idaho)

7.1 Verticillium dahliae (Early die)

Nematodes and Verticillium interaction is an important factor in the Colombia Basin, where around 80% of potato land is treated with the soil sterilant, metham sodium, to combat nematodes and early dying. Interaction research (fungus with nematodes) is difficult and trials performed across the USA have given conflicting conclusions.

Dr Jim Davis has a large experience with early dying disease. He feels that the "normal" starting point of investigations, diagnosis of Verticillium dahliae from the field, is not a useful piece of information. Verticillium is so widespread that most samples will show positive, giving little indication of its significance. He recommends a laboratory assay approach. The right assay equipment is essential to measure colonisation and then relate this to yield. The "Anderson Sampler" ($US 2 000) is an excellent piece of equipment for this purpose (see technical paper). The Anderson sampler can be used to standardise assay techniques for a range of diseases, including Colletotrichum, Fusarium and Verticillium. Dr. Dennis Johnson (see references) used the sap-squeeze technique as an alternative to the Anderson Sampler.

Dr. Davis has found that although most of the metham sodium is applied commercially through irrigation water with centre pivots, it works much better if it is injected 15 cm (6") deep with shanks 30 cm (12") apart and then rotovated (can be cross-disced) and lightly watered . The soil should be moist before injection. When applied in this way (at 50 USgallons /acre), metham sodium does a good job on the soil-borne phase of Rhizoctonia as well as nematodes and Verticillium.

Dr. Davis presented a paper at the PAA Conference: "Investigations of the role of Verticillium

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tricorpus in the biosuppression of Verticillium wilt of potato". This paper reported that both V. dahliae and V. tricorpus are found in Idaho potato fields - easily distinguished on NPX agar. Dr. Davis reported an inverse relationship between V. tricorpus and Verticillium wilt, and a positive relationship between V. tricorpus and yield. Dr. Davis also notes that this is a common observation in the field. Greenhouse trials (inoculation) have found similar relationships. Yield increased 15% with V. tricorpus. V. tricorpus was multiplied and added to fields in alginate pellets (60kg/ha). This gave suppression of wilt, but unfortunately V. tricorpus can be a mild pathogen of Russet Burbank and increased the number of deformed tubers. The researchers are not optimistic about the prospect of V. tricorpus as a biocontrol agent for V. dahliae, but are very optimistic about the future of biocontrol of V. dahliae using a range of organisms combined with green manure crops.

Dr Doug Rouse is conducting field research looking at Verticillium dahliae and Pratylenchus nematode complex. Verticillium is currently combated in Wisconsin by rotations (up to 4 years) and metham sodium in bad cases. Verticillium is worst on sandy soils, entering the plants through the roots. Dr. Rouse is examining the view that Verticillium, Pratylenchus and PVY combine in a disease complex to cause the serious problems often noted in commercial crops. PVY has been found, in early research, to greatly enhance the debilitating effects of Verticillium.

7.2 Colletotrichum atramentarium (Black dot)

Black dot disease caused by Colletotrichum fungus has been a subject of controversy in the USA, as in Australia. Several researchers believe that the organism is a secondary invader of previously stricken plants. Dr. Dennis Johnson believes black dot to be an important pathogen, capable of causing severe yield reduction in its own right. He has found that the foliar phase of black dot causes a 10% yield reduction if active in Washington State potato crops. Losses caused by the soil phase are unknown. Black dot incidence and effect is made much worse by any other accompanying stress, especially in Russet Burbank. Black dot is known to live on many weeds and is hard to research because controls are often infected, even plots treated with methyl bromide. In glasshouse trials, plants wounded (by sand blast) were found to be more vulnerable to black dot infection. In two glass house tests, foliar inoculated plants suffered 32% and 19% yield loss.

In 1991 plants (Russet Burbank) were inoculated in the field and then irrigated for 10 minutes in every hour for 12 hrs. Healthy plots yielded 8% more (total tuber weight) than inoculated plants. This is probably an under-estimate of losses since the controls also contracted black dot. Dr. Johnson has also noted that black dot appears to act in concert with PVY and Verticillium to cause serious losses.

Two fungicides; Fungines® and Rally®, help to combat black dot. None of the early blight products tested have controlled black dot. One problem with fungicides for black dot control is the timing of applications. After severe sand blast is most important. Potato crops in the south east of South Australia are often subject to severe sand blast and it is very possible that the early dying of Russet Burbank often encountered is the result of a black dot/pvy I Verticillium complex.

Dr. Davis says that Vapam® (sodium metham) doesn't successfully control Colletotricum when applied with a centre pivot.

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7.3 Helminthosporum solani (Silver scurf)

Silver scurf is an increasing problem in potatoes in the USA. Silver scurf is not effectively controlled (currently) in USA potato crops with chemical treatment or resistant cultivars. Resistance to thiabendazole is widespread. Methyl bromide will be banned in USA by 2000 (badly depletes ozone). Imazolil sulfate (Imazolil® - Janssen Pharmaceutica - Belgium) is performing reasonably as a seed treatment.

Silver scurf is worst in the USA for early plantings with delayed harvest dates. Work at the University of Idaho Research and Extension Centre, Kimberley, conducted by Ms. Mary-Jo Frazier and Dr. Gale Kleinkopf has found that Topsin® and Mancozeb® are good for silver scurf control. The combination is more effective than any one chemical against silver scurf. Although Topsin® alone has not done better than control it is thought that the combination with Mancozeb® is better than Mancozeb® alone. Maxim® (new Ciba Geigy product) looks very promising on silver scurf. It is not known if the silver scurf organism causes yield loss in addition to cosmetic problems; work planned may reveal this next year.

Dr. Kleinkopf noted that Maxim® also appears to have good performance against Fusarium as well as silver scurf.

New work, reported at the PAA Conference by Dr. Steven Vaughn (National Centre for Agricultural Utilisation Research, Peoria, Illinois) has found that silver scurf is inhibited by brassicas grown before the potato crop. The ruptured leaves contain ally! isothiocyanate and other glucosinolates. The active glucosinolates are more toxic to silver scurf than commercially available chemicals. Brassica juncea and B. nigra have good levels of the glucosinolates. Rapeseed (B. napus) will also suppress root-knot nematode when worked in as a green mature.

7.4 Potato virus Y

Potato virus Y has emerged as an increasing problem in recent years. Dr. Jim Davis (and several others) think that the potato cultivars Shepody and Russet Norkotah are latent carriers of PVY. Problems with PVY on Russet Burbank have only become major since Shepody has been cultivated. Shepody is harvested early and aphids move to later maturing Russet Burbank, leading to infection. Keeping 1" off seed from Russet Burbank crops in this situation is asking for real trouble. Interaction between Verticillium and PVY can be demonstrated strongly for PVY introduced by aphids in the same season. Yield losses are big.

Dr. Doug Rouse also reported that Russet Norkotah is very susceptible to early dying and carries PVY. The virus enhanced the symptoms of Verticillium greatly.

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7.5 Fusarium

Fusarium sambucinum and Fusarium solnai have been found to be resistant to thiabendazole (Mertect®) and thiophanate methyl (Topsin®). Dr. Phil Nolte (University of Idaho, Idaho Falls) found in tests in 1992/93 that 78% of growers were dealing with resistant strains. The current strategy for growers is:

- Use fungicide combinations. - Use IPM practices to reduce disease pressure. - Don't store cut seed for longer than 2 weeks*.

* Some US growers pre-cut 4-6 weeks ahead of planting, this is probably a contributing factor to resistance.

Work is in progress examining biological agents that control Fusarium which have been found in soil extracts, including bacteria (Pseudomonas and others).

7.6 Rhizoctonia solani (Black scurf)

Little active research on Rhizoctonia was encountered on the study tour. A large amount of research on the disease has been done previously, notably by Dr. Jim Davis. Dr. Davis has produced several publications on Rhizoctonia, including one examining the influence of the disease on optimum plant densities which found that wider plant spacings can be used for Russet Burbank if the disease is controlled - i.e. Russet Burbank should be planted closer where Rhizoctonia is expected to be a problem.

Work on Rhizoctonia in Australia should begin by sorting out the strains. Dr. Jones has found that Rhizoctonia that grows on alfalfa (AG-4) doesn't attack potatoes (AG-3). AG3 and AG4 are both strains of R. solani.

7.7 Alternaria solani (Early blight)

Early blight is viewed as a serious problem for the potato industry in the USA, mainly due to the enormous amount of chemical used routinely to control the disease. At the PAA Conference it was reported that west of the Mississippi 60-90% of potato crops are treated for early blight (2-5 sprays). Yield loss ranges from 5-40% without treatment. East of the Mississippi 100% of the crops are treated, with 25-50% yield loss without treatment. In 1990, 526,000 ha (1.3 million acres) of potatoes were harvested in the USA, yielding 20 million t, worth $US 2.2 billion. The estimated cost for fungicide applications on North American crops is greater than $US 21m and can exceed $US 44m in a bad year.

Societal concerns about these sprays are growing: Worker safety, consumer safety, environmental safety (groundwater, drift). The potato crop is a vulnerable target for future cuts in pesticide use and resistant cultivars may become a necessity. The technology and gene-pool are available for making the needed advances. Russet Burbank has less resistance than many new lines in breeding programs and testing for resistance to early blight is now a major part of breeding programs. The frequency of fungicide applications can be safely reduced on moderately resistant cultivars. There is an interaction between early blight and Verticillium resistance.

In addition to resistant cultivars, a large effort is being placed in the integrated management of early blight and the rationalisation of chemical control. Key areas used for integrated pest

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management programs are: Site selection, crop rotation, crop nutrition (nitrogen deficiency in particular leads to greater crop susceptibility), careful irrigation (leaching of nutrients), and the management of other pests to avoid stress.

"P-day" (physiological days) model has been developed to predict early blight sporulation, allowing reduced chemical inputs.

Common fungicide treatments used on commercial crops are: Bravo®, coppers, Rovral®, and Mancozeb®. All of these can only slow the epidemic and give approximately 15% yield benefit in typical USA potato crops. Zinc is reputed by some researchers in the USA to improve the efficacy of Bravo® for early blight. Dr. Trevor Wicks has tried this in Australia and found no benefit.

7.8 Streptomyces scabies (common scab)

Biological control of common scab using suppressive strains of Streptomyces is being investigated. In a paper at the PAA Conference it was reported by Dr. D. Liu (University of Minnesota) that some soils are known to be "suppressive" of common scab activity, but lose this property when autoclaved. This indicates a biological agent may be responsible for suppression of 5. scabies. Further examination found four isolates of Streptomyces were found to be antagonistic to 5, scabies. These were grown on vermiculite + food to use in field tests. The trials used Norchip, a variety with some resistance to common scab (to allow easier counting of the lesions). All tests with isolates were successful in reducing scab. 5. fulvoviolaceus ("PONSSII") was very good. It is possible that this approach may lead to a commercial approach to controlling the disease.

7.9 Nematodes

Drs. Jerry Santo and Hassan Mojtahedi head a team working on nematodes at Prosser. The team researches nematodes, tests soil for nematodes and tests new nematicides. Main interests are Meloidogyne chittwoodi, M hapla and stubby root nematode. Control measures in Washington State for nematodes in potatoes cost $US 20m annually. Without control, losses would exceed $US 40m.

M. Chittwoodi produces warts on the tuber. A thin peel of skin from the tuber reveals pin head flecks (pale brown) which develop after the deposition of eggs. The larvae do not move through the tuber. These are examined using a bleach stain procedure (see article). The nematodes develop further in storage, even under low temperatures (M. hapla is inactive below 10°C, M. chittwoodi below 5°C). Infected tubers are sold fresh or processed immediately. Nematode testing of tubers is a big business in the Columbia Basin area. M. hapla produces internal blemishes. Stubby root nematode is a vector of virus, producing concentric rings.

Control is by soil fumigants + Mocap® (to kill shallow populations). Nemacur® is not registered in Washington. Two soil fumigants are commonly used: Telone® (20 USgallons/acre), shanked 45 cm (18") deep in autumn, and metham sodium, which is applied through centre pivots in autumn. Combining the two gives deep and shallow nematode control and early die organism control.

Very few growers use Telone® + Vapam® + Mocap®. If growers use only Telone®, they may still have a Verticillium problem. Most growers use Vapam® and Telone®. Vapam® at 50 USgallons/acre, Telone® at 20 USgallons/acre - which costs $US 300 - $350/acre for both. It is possible to lower rates if they are used in combination. 15 USgallons/acre of Telone II® + 40 USgallons/acre of Vapam® has been proven effective in trials.

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Vapam® does not work well injected in the soil unless it is done in broad bands. Vapam® is most commonly applied through the irrigation system with 25 mm (1") of water. Soil should be pre-wet to aid movement. Vapam® does not move well in some soils. Surprisingly, some of the worst failures are on sandy soils.

Recent work has examined the benefit of certain crops for the suppression of nematodes. Green manure (wheat) followed by rapeseed before the potato crop, has been found to reduce nematode tuber culls by 80%. This is not yet acceptable to processors. Rapeseed and Mocap® has also given good results (as good as Telone®). The rapeseed is incorporated one month before planting, Mocap® is put on at planting. Sudan grass + Mocap® also does a good job. (See publications).

Problems exist with this approach, however, some of the growers see rapeseed as a weed as it is hard seeded and must be worked in before seed set. If Mocap® is used too often it leads to a build up of bio-degradation agents.

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8.0 Insects

Insects generally represent a greater problem for potato crops in the USA than in Australia, and a greater amount of insecticide appears to be used on potato crops in the USA, including several systemics applied routinely at planting. The Colorado potato beetle, in particular, represents a significant challenge to potato entomologists. Most of the large potato research teams include an entomologist.

Valuable sources of information on insects of potatoes were:

- Dr. Gary Reed (Hermiston Agricultural Research and Extension Centre, Oregon State University, Hermiston, Oregon)

- Dr. Jeff Wyman (University of Wisconsin, Madison, Wisconsin) - Dr. Larry Sandvol (University of Idaho Research and Extension Centre, Aberdeen, Idaho)

8.1 New systemic insecticides and transgenic potato cultivars

Systemic insecticides applied at planting are very important in the USA, unfortunately insect resistance to the products in common use is widespread. A large program at Hermiston (Oregon), run by Dr. Gary Reed, is examining several new systemic pesticides. The major pests at the trial site at Hermiston are: Aphids (green peach aphid {Myzus persicae)) and potato aphid {Macrosiphon euphorbia)), Colorado potato beetle (Leptinotarsa decemlineata), wireworms and nematodes.

Commercially aldicarb (Temik®) was used up to 1989, but it has been de-registered. Currently Thimet®, Disyston® and Furudan® are used commercially. Disyston® and Thimet® are very similar chemicals. There is already widespread resistance to Thimet® and resistance to Disyston® may soon follow. Both are used pre-plant or at planting and followed up with granular post-emergent applications.

A transgenic Russet Burbank, with the Bacillus thuringiensis gene (Bt.t) is being field tested at Hermiston and Hancock (University of Wisconsin, Madison). The Bt.t transgenic potato reproduces the toxin produced by the B. thuringiensis bacteria, in the plant. It is a mandibular arrestant, immediately halting feeding. The toxin in the potato tuber is reputed to be harmless to humans (from rat testing and limited human exposure). Dr. Reed's research is looking at leaf and soil fauna to see if the B. thuringiensis transgenic leads to any secondary effects.

A significant new product from Miles {= Bayer) is being tested by Dr. Reed and will be called "Admire®" (= Confidor®), a nicotine related compound.

Three methods have been tested for applying Confidor® to the soil:

1. In furrow. Fluid run into the furrow at planting at seed level. 2. 17 cm (7") band applied in furrow under the tuber at planting. 3. Side-dress soon after planting.

The 17 cm band has proven to be the best. The recommended rate - 3.3 kg product/ha (31bs product/acre). Little damage to predators and parasites is apparent when Confidor® is applied in this way. Confidor® is giving excellent control of Colorado potato beetle and aphids. Control of soil insects (wire worm) has not been good, despite company claims. Confidor® is not good against Lepidoptera.

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Other chemicals being tested include:

-"ASC66824" by ISK (Japanese Co.), a good nematicide with control of Meliodogyne hapla, M. chittwoodi also giving good aphid and larval Colorado potato beetle control. It is soft on predators.

-"CGA215944" (Ciba Geigy), an aphicide, going very well. For some reason the plots have more late blight than the Di-syston® treatment - this is consistent through the trial.

-Permethrin has performed poorly and has been responsible for "resurgence" outbreaks of aphids.

-Vydate® is going well on nematodes, aphids and beetles, but is very expensive. Gives a growth regulator response and the plants look good. Sprayed on twice.

-Thimet® failed on aphids (resistance), but has performed well on Colorado potato beetle.

-Tri-guard®, a juvenile hormone, failed against Colorado beetle. It also affected predators leading to increased aphid populations.

-Novodor®, a "spray-on" B. thuringiensis formulation for beetles, is going well (not quite as well as the Bt.t transgenic potato). Novodor® has an ultra violet stabiliser.

Dr. Reed has found that potatoes lose marketable yield after 10-15% defoliation in mid growth, however up to 50% of leaf area can be lost before a great loss of total yield. Unfortunately in commercial crops efforts to control the chief defoliator, Colorado potato beetle, are the start of many other pests.

Economic thresholds are rarely on for potatoes in the USA, they are perceived as too difficult and expensive to formulate.

Dr. Larry Sandvol has also had experience with Confidor® and is impressed by the length of protection afforded, even at low rates. One strange observation he passed on was the effect of Confidor® on aphids when applied as a foliar spray - the aphid population increased, not due to resurgence but apparently due to an increase in fecundity! Dr. Sandvol has investigated the use of yellow flowering crops (such as yellow mustard/canola) as trap crops for flights of aphids. These plants can also be used when flowering in pots as aphid indicators near potato crops, in place of traditional yellow pans or sticky traps.

Dr. Jeff Wyman reported on the impact of transgenic Colorado potato beetle resistance on potato pest management on the PAA Conference field tour. Control of the Colorado potato beetle is the Achilles Heel of many integrated programs since chemicals applied to control this pest often lead to a series of following pests and the inevitable chemical treadmill. Consequently the development of the transgenic line is being hailed as a great advance.

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9.0 Weeds

Weed control in most commercial crops observed on the tour was excellent - no crops came close to the magnificent spectacle of some Australian potato crop struggling as mere undergrowth to a 2m forest of fathen and nightshade. Reliance on herbicides is the normal practice in north west USA, with as few cultivations performed as possible - to reduce damage to crop root systems. This is in stark contrast to the south east of South Australia, where various cultivations (and root damage) proceed well into tuber bulking.

9.1 Herbicides

Metribuzin (Lexone®, Sencor®) is widely used in the USA. Growers avoid spraying metribuzin on emerged potato crops if cloudy conditions are expected in the next two days since the potential for crop damage is reputed to be much greater. Metribuzin has a strongly differential effect on varieties, Russet Burbank is tolerant, whilst Shepody is very susceptible to damage. Potato growers in the USA also commonly use Dual® & Linuron®.

A new herbicide for potatoes from DuPont is Matrix®. Matrix® has shown very good results in 3 years testing. It offers pre- or post-emergent control for weeds in potatoes, including broadleaf and grass weeds. Matrix® doesn't control lambsquarter. Matrix® may be tank-mixed with metribuzin. This system gives control for most of the potato season. Metribuzin is not badly inactivated by hilling, but hilling moves chemicals to the hill where control is still given, leaving furrows unprotected.

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10.0 Tuber disorders

Disorders of the potato tuber are poorly understood and frustrating to research, due to their "hit and miss" occurrence. "Dark ends", "translucent ends", "sugar ends" and "jelly ends" are terms which are in common use to describe the reducing sugar disorder of the stem end of tubers, particularly of Russet Burbank, which results in dark tissue after frying (Maillard reaction). Internal heat necrosis, brown fleck, and internal brown spot are disorders which are not so clearly defined. Bruising remains a major concern for potato processing companies and large research and extension campaigns are run to reduce the problem.

Valuable sources of information on tuber disorders were :

- Dr. George Clough (Hermiston Agricultural Research and Extension Centre, Oregon State University, Hermiston, Oregon)

- Dr. Bill Dean (Irrigated Agriculture Research and Extension Centre, Washington State University, Prosser, Washington State)

- Dr. Clint Shock (Malheur Experiment Station, Oregon State University, Ontario, Oregon) - Dr. Jeff Stark (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Ian Gubb (Wye College, University of London, Genetics and Biochemistry, Wye, Ashford,

Kent) - Dr. Dale Westermann (University of Idaho Research and Extension Centre, Kimberley, Idaho).

10.1 Dark ends

The last ten years has seen a large number of publications on factors causing dark end problems in french fry potatoes. It is no coincidence that most of these articles also feature the cultivar Russet Burbank. Drs. Jeff Stark and Clint Shock maintain that although any stress on the plant can contribute to the dark end disorder, heat and water stress during tuber initiation and early tuber bulking are the main culprits. Recent extension publications for USA growers list many factors to be followed to avoid the disorder: Good rotations, maintenance of soil structure for good drainage and low compaction, rapid canopy closure, properly scheduled irrigation, good disease control

and so on ... it's that simple!

This disorder is well understood and may be deliberately induced in the glasshouse using heat or water stress treatments. I fear that many potato enterprises in the south east of South Australia may find this knowledge difficult to apply in practice.

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10.2 Internal heat necrosis (IHN), internal brown spot (IBS), brown fleck.

Several posters and papers were presented at the PAA Conference concerning these disorders and they all had one thing in common - conflicting or inconclusive results.

Calcium is often proposed as a major factor. Low calcium leads to poor integrity of the cell membrane, leading to increased soft rots and leakage of water and solutes. Potato tuber tissue is generally deficient in calcium. There is a threshold concentration of tuber calcium of 200ppm, below which a range of tuber quality disorders are more likely to occur. Unfortunately, tuber calcium is only taken up by stolon roots and the small tuber roots and is often more a product of vine growth (and calcium robbed from the tuber) than it is of available calcium in the soil.

Dr. George Clough has also examined the role of calcium. He finds calcium related tuber disorders are spasmodic and appear to be related to climate. It is worst in years of high temperature, leading to fast vine growth which robs tubers of calcium (especially when matched by high irrigation and high nitrogen). The problem can be worse in hot sands since tuber roots are a rarity under these conditions.

Dr. Clough has found tuber quality responses to applied calcium (even in "adequate calcium" soils) applied before planting and side-dressed, but again the results are not consistent from year to year. Amongst commercial growers, gypsum (pre-plant) and calcium nitrate have the reputation of beneficial effect on tuber disorders. Recent work by Dr. Clough is examining new calcium sources for side-dressing (variations of calcium and nitrate). Dr. Clough feels that calcium nitrate should prove best. An alternative is calcium-ammonium-nitrate.

Dr. Clough said that high irrigation rates lead to a dilution of calcium in soil solution in most areas of the USA where the irrigation water has little or no calcium. Calcium in the soil greater than 3 - 4 milli equivalents is normally felt to be adequate. Calcium in the petiole is not related to tuber calcium. There is a relationship between applied calcium and IBS and between applied calcium and tuber calcium. However, low calcium in tubers doesn't always lead to trouble, and high levels of calcium in tubers does not preclude problems. The problem is obviously more complex than a simple explanation in terms of calcium.

Boron has been proposed as a factor in IBS, but there is no genuine research support as yet. Boron is related to sugar translocation and Dr. Clough feels it may be related to the dark-end disorder. Potato growers at Hermiston normally apply boron.

There is also a variety interaction. Atlantic and Frontier Russet are susceptible to IBS and IHN, while Russet Burbank is moderately susceptible.

IBS is a particularly critical issue for the Atlantic cultivar. There are 2 distinct disorders; cortical tissue damage and paramedula tissue. Dr. Bill Dean feels that this could be related to the timing of the cause. It is also possible that the problem could be related to a pathogen. There is evidence that the disorder is plant specific rather than culture specific. IBS is rare on research stations compared to commercial farms. One thing these stations do is to carefully select seed from very good seed growers. The disorder is not related to leafroll, although a virus or mycoplasma is a possibility. This year Dr. Dean will perform research looking the "transmission of IBS" as a first step in examining this theory.

Hollow heart and brown centre are common problems in Eastern Idaho, caused by rains, heat and frost.

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10.3 Bruise

Dr. Ian Gubb feels that the potential to reduce the impact of black spot bruising by using genetic manipulation (transgenic lines) is great. There are wild solanums with no bruising, one of the major causal enzymes is missing. This enzyme complex also aids in pest and disease resistance.

Dr. Dean is leading a team working at Prosser (Washington) examining the chemical and physical basis of bruising and developing methods to quantify the bruise potential of cultivars. Dr. Dean said that Ranger Russet has a very bad black spot bruise potential. It has the same chemical bruise potential as Lemhi Russet and a worse physical bruise potential. Longer growing season areas lead to worse bruising. Ranger's reputation for bruising varies between growing areas.

Dr. Dean has found that, for many varieties, bruising problems get worse after yield has peaked and tops may still be green. A physiological change occurs in the tuber after the peak in yield and specific gravity, increasing bruise potential.

Black spot bruise publications are about to come out; Dr. Dean says they could "re-write the text book".

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11.0 Potato breeding/new cultivars

The most exciting papers at the PAA Conference at Madison were, in my opinion, those which outlined new developments in the development of new potato cultivars. The traditional potato breeding programs are still the major source of new cultivars, but have now been supplemented by a range of new technology, enabling the production of transgenic lines and precise genetic manipulation. World-wide many programs are now in operation mapping potato genes, searching for genetic material for insertion in the potato and developing the new technology of genetic manipulation for potatoes.

Valuable sources of information on potato breeding and new cultivars were:

- Dr. Al Mosely (Oregon State University, Corvallis, Oregon) - Dr. Michael Thornton (University of Idaho, Parma Research and Extension Centre, Parma,

Idaho) - Dr. Robert Thornton (Washington State University, Pullman, Washington) - Mr. Dan Hane (Hermiston Agricultural Research and Extension Centre, Oregon State

University, Hermiston, Oregon) - Mr. John Shields (McCain Foods, Othello, Washington) - Dr. Dennis Corsini (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Joe Pavek (University of Idaho Research and Extension Centre, Aberdeen, Idaho) - Dr. Steve Love (University of Idaho Research and Extension Centre, Aberdeen, Idaho)

11.1 Transgenic cultivars

Pest and disease resistance introduced to existing potato cultivars from other species, including bacteria, is now a major research theme in the USA. Transgenic lines with resistance to PVY and leaf feeding insects are already growing in field plots.

Dr. Tom German (University of Wisconsin, Madison) gave a paper at the PAA Conference which caused some heated discussion. He (and others) pointed out that, although a great pool of resistant genes was available in the 300 known species of solanum, including resistance to all major diseases of cultivated potato, the collection of these accessions and their examination was incomplete - due to lack of funds. Others at the conference pointed out that even if this genetic pool was available, little money was available to current breeding schemes for their incorporation. From the discussion, it seems that everyone can see the amazing potential of the new transgenic technology to improve the potato but funding had not yet caught up with the concept at the "hands on" potato breeding level.

Dr. David Spooner (University of Wisconsin, Madison) is examining wild solanum species in the field. Unfortunately the taxonomy of solanum species is "a mess". He is also involved in the maintenance of many solanum species "in captivity" in the USA.

Dr. Christian Gebhardt (Max Plank Institute, Germany) gave a paper concerning the molecular biological aids available to genetic improvement in potatoes. Mapping of resistance alleles in potato genetic material with RFPL markers is well advanced. These markers will be available as kits for breeders to use (similar to Eliza kits for virus). Without going into technical examples, it seems that basic research in this field has extended far beyond that being commonly used by potato breeders. This situation may lead to large private companies, with adequate resources, claiming this technology, producing transgenic lines and recouping funds by way of royalties. The money paid by potato growers for the right to grow new potato cultivars may rise exponentially The Australian potato industry should take note of this.

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Mr. Solomon Yilmaa, a PhD student working with Dr. Mosely at Corvallis, is using protoplast fusion techniques to gain genetic resistance from Solarium etuberosum (a wild solanum) for leaf roll virus. The protoplast fusion approach is working well and progress has been good.

Rhizoctonia Solani genes have been successfully introduced to canola in Canada with good results.

Dr Michael Thornton reported on the field evaluation of transgenic potato lines, transformed for high tuber solids content. Tuber solid content of transformed Russet Burbank lines (owned by Monsanto®) was between 21-25%, compared to 18-20% for the non-transformed controls. Some transformed lines had lower vigor and yields, however 30% of the high tuber solid lines were selected which were true to type with no loss in vigor. Plants grown from these selections in the following year again produced high tuber solids.

11.2 The North West potato breeding program

The co-ordinated North West USA breeding program and variety development program started in a small way in 1984. The program has been increased since, with the 3 states (Washington, Oregon and Idaho) pooling resources. This program gets $lm from the USDA/year, to be split between the three states for new potato cultivar development. The rest of the money needed comes from levies collected by the Potato Commission and state funds. Each state has a role, but all breeding is done in Idaho (Dr. Joe Pavek et. al., Aberdeen). This is a traditional breeding program.

Dr. Al Mosely is the project leader for Oregon State. Oregon gets true seed from Aberdeen, which are planted (several/pot) in the glasshouse. From 200,000+ seeds, 60,000 tuber families are produced per year (only Vb seeds produce a transplant). The resultant plants are transplanted and grown 1/pot in the glasshouse. Glasshouse potatoes are grown with low nitrogen to promote tuber initiation, which leads to a problem with early blight. The pot media is a mix of pumice and peat soil.

From each pot, 1 large tuber (lOg) is kept for further propagation. The smaller tubers are kept for insurance (in case the cool-stored big tuber is ruined).

Small tubers from the greenhouse are sent out for further single hill testing at four research stations in Oregon. Single hill research is conducted at Hermiston, Ontario, and two others.

In Oregon, from the initial 60,000 lines, VA-2% are selected, mainly on tuber appearance. After year 1 in the field, 900-1,200 lines remain. After Year 2 in the field (where 12 hill trials of selected lines are run), 150 lines remain. Almost all selections in the first two years are made on tuber appearance. In year 3 in the field, 2 replicates of 7.5 m (25 ft) row plots are grown. These trials are looking at tuber quality and disease resistance. After year 3, 40 lines remain. In year 4, 30-40 lines are planted at four locations in Oregon. Four replicates of 7.5 m (25 ft) row plots are planted at each location. These trials are looking at tuber quality and yield.

Some lines may stay at this stage for a couple of years. Lines with good prospects in year 4 are put forward for Tri-state trials. After this, surviving lines go to the Western Regional Trials (8-10 states). Survivors of this process are named and released. Dr. Mosely noted that the percentage of Russet types from Dr. Pavek's selections is increasing.

Idaho also has a full testing program as well as the breeding phase. Washington State is mainly

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known for agronomy research. Washington takes part in Tri-state and Western Regional Trials, but not in early stage trials.

Mr. Dan Hane runs the Colombia Basin part of the Oregon variety program at Hermiston. This starts with 12 hill stage (or sometimes 4 hill) for 150-200 lines. Hermiston is a good place for disease resistance testing of selections. It has a long season with high pest and disease pressure. Screening new lines for virus resistance is a special interest of Mr. Hane.

A series of agronomy trials are then performed for new selections headed for release, to fine tune the agronomy of each new cultivar (spacing x fertiliser x irrigation).

Research co-ordination is self policing and has worked out well. All players are connected by money trails, overseen by the USDA.

11.3 New french fry potato cultivars from the USA

Russet Burbank easily remains the major french fry potato cultivar in the USA. The Russet Burbank line "Williamson" is reputed to perform the best in Idaho.

Ranger Russet is a significant new french fry cultivar. Compared to Russet Burbank it has higher yield potential, better specific gravity, less hollow heart, is more resistant to Verticillium dahliae. and has similar early blight resistance. The negative points for Ranger Russet are that it is more susceptible to Colombia root nematode (Meloidogyne chittwoodi) and it is more susceptible to black-spot bruise.

Frontier Russet, another recent french fry release is probably not suited to growing conditions in south east South Australia. It is susceptible to internal brown spot and heat necrosis, has a poor canopy, low tuber set and large tubers. Frontier Russet has performed poorly at several test locations in the USA, including Hermiston.

New french fry lines showing promise in advanced testing at Hermiston (indicated by Mr. Hane) are:

- A082611-7 - COO83008-1 (processes well with few internal defects, but is a bit short) - NDO2904-7 (early maturing variety) - A84180-8 (early maturing variety)

Dr. Robert Thornton likes the chances of A82119, an Aberdeen selection doing very well. It is very blocky and not as rough as Russet Burbank and it is a good processor with high yield, good specific gravity, and is not highly susceptible to Verticillium wilt. It has four more years before naming and release.

Mr. John Shields has found, from the processor's point of view, that Ranger Russet has a better specific gravity than Shepody (1.09's vs. 1.085), but bruised as badly as Lemhi Russet. The bruising problem has ruled Ranger Russet out as a storage variety. Ranger's harvest period follows Shepody and fills in for 30 days until the main Russet Burbank harvest period. Ranger is blockier than Russet Burbank and has very good recovery for the processor. It is longer than Shepody. Mr. Shields said that Nooksack and Highlite Russet are not long enough for the new tuber specifications for french fry processing. He is not impressed with Goldrush; it has poor tuber shape in the Colombia Basin, but has performed better in the Mid West.

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Dr Dennis Corsini has had experience with Nooksack, a variety that performs weii under harsh sandy conditions in south eastern Australia. Dr. Corsini says Nooksack has no more sugar problems in the tuber than Russet Burbank and is less prone to bruising. Nooksack stores as well as Russet Burbank and needs less sprout inhibition. Seed management is critical for Nooksack, dormancy must be broken. Pre-cutting may help break dormancy. Nooksack has problems with seed piece breakdown under wet conditions, probably due to a poor suberisation mechanism. Low yields result if a fast, even emergence is not attained. Nooksack is resistant to Sclerotinea and is moderately susceptible to Verticillium and early blight (although less so than Russet Burbank). It is important to maximise stem numbers by seed management for Nooksack. Nooksack gives a good processing recovery due to its blocky shape. Hollow heart is less of a problem in Nooksack than Russet Burbank. 30 cm (12") in the row is the maximum spacing for Nooksack near Aberdeen. Small tuber size is a problem at Aberdeen, where the growing season is only 120 days, but wider spacing than 30 cm doesn't help. This issue must be checked for each area. There is Nooksack (tube stock) available in Idaho if it is not in Australia.

Dr. Steve Love is a member of the Aberdeen potato breeding team. His job is the agronomic fine tuning of varieties before release. If new lines are not able to fit in with existing common agronomic practice, they are discarded. Some new cultivars need substantial management changes, but most fit the farmer's capacity. Dr. Love said that the best seed storage temperature for Nooksack is 10°C, to ensure good emergence. However, at this storage temperature some tubers sprouted, so a practical solution may be 7-8°C. Nooksack stored at 3°C is difficult to bring out of dormancy evenly. Dr. Love has found that overall less nitrogen needs to be applied to Nooksack than Russet Burbank. Commercial yields of 44 t/ha (350cwt/acre) were achieved for Nooksack on silt loams. Nooksack is generally resistant to problems that cause early death -Verticillium, Black Dot, and early blight, but Nooksack is susceptible to virus.

Dr. Love gave his opinion on french fry varieties that may do well under harsh, sandy conditions (below). In general, french fry cultivars that do well in these conditions have large vines and are late. Some promising types fitting this description are:

- A82119-3 - A81473-2 short tubers. - A7961-1 a medium maturity, long Russet that has performed well over a range of soils. -A84118-3 a long russet, resistant to bruise, strong vine, stores well and an excellent

processor. - A84180-8 an early Russet (earlier than Ranger), tubers are well developed before vine death,

processes well. - C0083008-1 may be particularly good for harsh, sandy conditions. - A7961-1 similar to Shepody, but has better yields and solids. Simplot are moving quickly

with this to replace Shepody. - A84118-3 a good late maturity selection. - A083037-10 a Nooksack cross, with many similar characteristics but higher yielding. Is a good

processor. Dormancy not as strong as Nooksack.

West Texas variety testing results should be of interest to the south east of South Australia -conditions may be similar. See "Western Regional Potato Variety Trial Report".

Transgenic bruise resistant Ranger Russet is a good possibility in a few years.

Agrico Holland have developed Agria (PVR), a potential replacement for Russet Burbank. Agria has good disease resistance, is later than Russet Burbank, yields better but has very yellow flesh.

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Although tests for cooking quality out of 4°C, are routinely performed for french fry cultivars at Aberdeen, the current emphasis remains how the cultivar cooks out of 7°C (45°f).

11.4 Red fresh market potato cultivars from the USA

Astonishment - the term that describes response in the USA when told that the Australian red ware market is mostly Pontiac.

Red Norland (an old selection) is a common early red variety grown in the USA. Several cultivars may be worth examining for use by fresh red potato growers in south eastern Australia:

- Rhine-Red a scab resistant red, which has storage problems. - Redsen a very dark red. - LA1259 a recent release from Louisianna is well worth testing. - Sangre selected in a cool area of Colorado. - Chieftan a good red fresh market variety from Iowa, has wide adaptability and good yield.

The tubers are the right shape, with shallow eyes. - Fontenot a new red variety (2 years since release), very red, heavy set, small tuber size,

performs well on sand, open availability (from Louisianna).

A large seed and fresh market grower encountered at the PAA Conference from Nebraska (hot growing conditions, sandy soil) noted that Sangre was a bit brown, not bright red, under their conditions. He liked Fontenot.

Oregon is currently developing new lines for the red fresh market.

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12.0 Storage

The possibility of the future de-registration of CIPC in Australia and the USA has caused a flurry of activity to find sprout inhibiting chemicals for use in storage to replace CIPC.

Potato storage is a very important issue in the USA, where individual potato enterprises often had temperature controlled potato stores exceeding 10,000 t, with more than 200,000 t capacity on one large property (Agri Northwest).

Valuable sources of information on diseases of potatoes were:

- Mr. Mike Lewis (University of Idaho Research and Extension Centre, Kimberley, Idaho). - Dr. Gale Kleinkopf (University of Idaho Research and Extension Centre, Kimberley, Idaho).

Genetic engineers are working on control of the sugar enhancing gene (cold temperature expression). Traditional breeding in the US has been cooking potatoes out of low temperature, but still class it as a low priority in french fry cultivars. There is no variety yet released from traditional programs for french fries that will cook satisfactorily out of 4°C (42°f) storage (only 2 crisping cultivars have passed). Cooking out of 4°C store has other advantages than the sprouting issue; there is less disease development and less shrinkage at this temperature. Progeny from lines that cook well out of 4CC don't inherit the trait well; multi genes are involved.

The Orida processing company runs their stores at 7-8°C for Russet Burbank. The Simplot stores are generally run at about 8-9°C for Russet Burbank. Shepody is not a storage variety, but is run at 10°C if needs arise - it is more sensitive to sugars at low temperature than Russet Burbank. Attempts to store Russet Burbank at 9-10°C have shown this to be risky; breaking dormancy faster, increased shrinkage and increased disease potential. The higher temperature leads to less sugar problems and faster reconditioning. Reconditioning is only occasionally needed (when sugar problems emerge after storage).

Optimal potato store conditions vary between regions and are dependent on tuber conditions out of the ground. On farm storage may represent 100% of the crop for some growers in the USA, but is most often in the range of 40-60% of crops.

Mr. Lewis feels that despite recent progress, suitable replacements for CIPC may be further away than 4-5 years for US registration - maybe 10 years away. He is testing 3 new compounds:

- DIPN (Di-isopropyl naphthalene)

- DMN (Di-methyl naphthalene), a natural chemical found in potato stores, produced by the potato

- Salicylaldehyde, from aspirin production

DIPN and DMN can be bought commercially. So far DIPN has looked the best option. It is applied as an aerosol using the same equipment as for CIPC, however thermal fog technology is better.

Fan speed for CIPC distribution has been slowed in recent years (to about 10-50% of normal, depending on the design of the plenum) to aid distribution efficiency.

Carvone, a new anti-sprout from the Netherlands, is soon to be released. It is produced from terpenes in caraway seeds and may induce off-taste in potato from its strong smell.

Eucalyptus and cinnamon extracts also work. McCains (Canada) is using 1-8 cinnaol (See Am. Pot. Jnl. Article June, 1993).

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13.0 Processing

Mr. John Shields (McCain Foods, Othello) said that typical deliveries of Russet Burbank potatoes from the Columbia Basin to the McCain Othello plant contain 93% "payables", consisting of 88% # l's and 6% undersized ($30 US/T). Tubers are graded according to USDA US # 2 for processing grade (external defects) and USDA US # 1 (internal defects). An x-ray machine is not used for hollow heart as it is not a big problem in this region. An ADR (optical defect machine) is mainly used to take out bruise from storage.

Tuber shape is emerging as an important current and future issue for the processor. Shape determines % recovery; length is especially important along with blockiness, since rounded shoulders lead to reduced recovery. Internal tuber quality is still a concern. Processors using material from the Columbia Basin have noticed solids have slipped in recent years as growers no longer have access to virgin ground. Sometimes loads can be blended to help a grower - this may be done for size, shape, specific gravity and nematode but not to mask fry colour or bruise. Otherwise lower quality tubers may be used in products that mask the problem, such as battered fries.

A large number of the potato growers supplying McCain Foods at Othello use crop management consultants and McCains have noticed the better results (consistency) from these growers.

An informal discussion held with members of the Aberdeen Research Centre on processing potato costs and returns was interesting. The cost of production in eastern Idaho is about $US 1 500 per acre (all up including interest and depreciation). Gross margin costs are about $US 1 000 per acre at 44 t/ha (350cwt/acre). Full season Russet Burbank (not out of store) bring around $US 5.00 US/cwt = $US 100/USt. Enterprise margin is $US 1 750 minus $US 1 500 = $US 250/acre at 44 t/ha (350cwt/acre). 500 acres is the maximum size in this area for one-man management (with some hired help). Potato areas bigger than this don't thrive without sons or hired managers.

The yields from the Columbia Basin are generally much higher, but the price paid by the processors for that area is lower. Price for mid season Russet Burbank is about $US 85 /USt (delivered, including bonus etc.). In general, a grower must exceed 28 USt/acre to survive. Processing companies operating in the region include, Simplot, Lamb-Weston, Nestle-Carnation, McCain Foods, Universal Frozen Foods, American Fine Foods, Twin City, Orida.

Simplot (and other processors) still buy potatoes in eastern Idaho (despite cheaper supply from Washington) to spread risk, time of supply and because of high tuber quality from Idaho. Colombia Basin can have specific gravity problems, in particular, and is often viewed as an early supply area.

Dehydration plants help the economics in eastern Idaho; rejects bring around $US 1.50/cwt.

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14.0 NASA and potato research

Several papers were presented at the PAA Conference which were part of NASA space research efforts. The production of potatoes in space is a serious issue for the long term space travel plans of NASA. The cost of transporting life support needs to the moon is $ US 11,000/kg. The life support payload can be enormous for extended stays in space :

Daily requirements/man (gms) 640 dry food 860 Oxygen 1270 water in food 2360 water drinking 1140 chemical to remove C02.

Plants do most of this ; C02 absorbed, 02 released, water purified (transpired), food produced.

Daily nutrition required/man (gms) 450 Carbohydrates 130 Protein 60 fat trace minerals trace Vitamins ? bulk

Advantages of potatoes - High production of digestible food, high harvest index, good carbohydrate and protein source, widely acceptable food, little processing, variety of culinary forms, extensive background knowledge, easily propagated in sterile culture.

The research, aimed at maximising potato production in a closed system under weightless conditions and unusual daylength regimes has turned up many remarkable facts on potato growth which may help solve problems on earth.

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15.0 Consultants

The use of crop management consultants was very common in the Columbia Basin in Washington State. Almost all crops employed irrigation scheduling consultants, with lesser numbers employing pest and disease scouts. The margins for potato production in this area are very slim and yields must exceed 28 USt/acre for the enterprise to remain viable. The potato growers leave little to chance, measuring many aspects of crop growth weekly and fine tuning their management in response to the information.

15.1 Professional Agricultural Services

A very large crop management consulting company operating out of Pascoe in the Columbia Basin is Professional Agricultural Services. This company is run by Mr. Mike Stephenson and Mr. Roger McCary.

The service started 11 years ago, mainly scheduling irrigation for potato crops:

Yr 1 4,500 acres potatoes managed Yr2 6,500 acres Yr3 8,000 acres Yr 11 (now) 18,000 acres of potatoes managed by 2 partners + 5 field men. + 10,000 acres other crops (vines + apples).

I spent a day with Mr. Stephenson as he read neutron probes. The vehicle was a large V8 Pickup, equipped with mobile phone, 2-way radio, mobile computer, printer, and neutron probe. The printer and computer are kept in a compact, fold out padded samsonite type of brief case and little time is needed since the printer and computer are permanently connected. The business runs to a tight schedule, and many small innovations reflected the "time is money" approach - the calculator hanging from the visor so that it was always on hand, the note book stuck to the window so that notes could be scribbled from the driving position....and so on.

Services currently offered are infra red photography, soil moisture (neutron probe), petiole and soil analysis, pest and disease scouting.

Pre-plant soil analysis includes major and trace elements. Post-plant analysis of soils is common place and is used as an aid to petiole interpretation, especially to make nitrogen fertiliser decisions. Post-plant soil analysis and petiole analysis is normally done weekly. Most post-plant soil analysis only looks at nitrate nitrogen, but can include phosphorus, potassium, sulphur, boron and zinc.

The neutron probe is read twice a week for potato irrigation scheduling in the Columbia Basin. Neutron probe advice is given in inches per foot. Monitoring is done to 3 feet, each foot reported separately. 2-3 sites are used per pivot paddock (about 40 - 50 ha). Normally the probes are placed in one dry and one typical site. Readily available water in this sand is about 85 - 115mm/m (1.1 - 1.5"/foot), wilting point is assumed to be 60% of this. About 70% depletion is allowed in the sand. Root zone for Russet Burbank is 45 cm (18") in loamy sand. Mr. Stephenson observed that neutron probe services that don't look at the whole crop and the irrigation system, fail.

Typically 700 - 750 mm (28-30") of water is applied on the sandy soil types per Russet Burbank crop in the Columbia Basin. 650 - 700 mm (26-28") is applied on sandy loam soils. The centre pivots generally apply 10 - 14 mm per circuit using a 24 hour rotation. 5 irrigations are applied

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per week in hot weather.

The neutron probe is calibrated to each soil type. Each site on a pivot may have a different calibration. Sand, silt, clay analysis is used to distinguish soil types. Problems with the neutron probe include neutron loss in the top 30 cm, and tuber water effect (tubers are 80+% water). The neutron probe is used for daily advice and for showing long term trends. Some growers are told what to do, others are given charts to interpret for themselves. The consultant must know what the grower wants.

The service is very fortunate - the crops are close together and we read 2-3 probe sites for 8 crops in 2 hrs. Mr. Stephenson also digs up soil with a spade at each site and feels the moisture. In addition, he examines tuber lenticels for evidence of moisture status. In some days one person covers about 40 crops with the neutron probe.

Infra red photos are used to identify areas of general crop stress, in particular, water stress. Some clients use them weekly, others 2-3 per season. Each photo costs SUS35. The infra red photos are used to detect soil variations, water patterns, bad outbreaks of pest and disease.

Professional Ag. Services owns its own irrigation program software. A range of data; weather forecast for next 5 days, neutron probe readings, etc. is entered. The program already has soil type, planting date, variety, emergence date, end use, mm/lap/time entered for each crop. The program calculates advice; how many hours to run, when.

Recently Professional Ag. Services took on a Government sponsored scheme to provide irrigation scheduling for new clients. It was free to the clients, but gained few clients. Two issues are blamed - "free service" perceived as no good, and government management of the scheme.

The service employs one man full time on pest and disease scouting - he gives a weekly report. He does not tell growers exactly what to do, but "paints the picture". Hard recommendations often lead to court in the USA. Pest and disease scouting time is about 1 hour per 50 ha field. This may come down as the field is "learnt" and trouble spots identified.

Professional Ag. Services allows the purchase of partial service, e.g. Infra red and soil moisture without the others. Only Va of the area managed uses pest and disease, all areas use irrigation scheduling, Va acres use nutrition. Visits to fields are not used to perform several jobs. Neutron probe, petioles, pest and disease are all done by different people. This is possible where distances are small.

Mr. Stephenson feels that part of their continuing success comes from the customers wanting advice divorced from sales. They want independent management advice. In addition some fertiliser and chemical representatives in this area are not reliable, they often fail to come on time.

Professional Ag. Service charges are all based on 40 ha 4- crops. The service has only had 2 bad debts over the last 11 years (small ones) - both with "outsiders" who were pushed into the service because of problems (by financiers).

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16.0 General notes

This section includes some information of a general nature encountered on the tour. Much of it was picked up in casual conversations and should be treated with caution.

16.1 Russet Burbank, Shepody, Nooksack

Small tubers (less than processing limits, < 100 g) represent about 15% by weight in commercial Russet Burbank crops, even well grown heavy yielding crops. Many growers do not realise this because the smalls drop through the chain. Russet Burbank in Idaho is reputed to do best with 10-12 tubers set/plant. More than 15 tubers per plant will have a negative influence on tuber size. Russet Burbank is not necessarily planted further apart in the row in poor sands in the USA -yield potential may not be less.

Wide spacing for Russet Burbank (30 - 37 cm (12 - 15")) can lead to stress syndromes; excess vine growth, poor canopy - leading to late cover and temperature problems, knobby tubers.

Shepody will grow as long as Russet Burbank if allowed to in Idaho. If left too long, specific gravity will fall and no more yield will result. Specific gravity of Shepody peaks at 120 days and falls away quickly after this. Unfortunately aphids from Shepody leave at harvest and settle on nearby green Russet Burbank stands. Growers keeping one-off seed from these crops run a big risk of PVY infection in the following crop. Shepody is a no - symptom carrier of PVY

Growers feel that Shepody is more drought tolerant than Russet Burbank. Research examining drought and Shepody (Dr. Clint Shock) found similar yield loss to Russet Burbank with water stress, but better tuber quality was maintained.

Shepody pieces must be cut bigger than Russet Burbank; 56 - 84 g (2V£-3oz) pieces. Shepody is generally planted closer - about 10 - 12 cm (8-9") in the row.

Shepody is very susceptible to early blight if nitrogen is allowed to run low later in the season.

Nooksack is often held at 22°C for 2 weeks to complete dormancy. Nooksack stores well and needs little (if any) anti-sprout CIPC. Nooksack seed should be cut large, about 70g (2.5oz). It is grown at an in-row spacing of 8-10" in Idaho. Nooksack is reputed to perform best under fertiliser strategies giving low nitrogen at planting. This leads to early tuber formation. Grow to tuberisation, then 2-3 kg nitrogen/ha/day is applied through the pivot. Nooksack, like Shepody is normally reserved for difficult or infertile paddocks.

16.2 Commercial practice

Columbia Basin potato enterprises (french fry) need to be at least 200 ha (500 acres) to be economically viable. Growers in the Columbia Basin commonly use 6 row pick (needle) planters and harvest with 3 row harvesters. All potatoes in this area are grown under centre pivots; 50 ha is a typical pivot size. Potato paddocks in Eastern Idaho are generally smaller, often using side-roll irrigation.

Normal practice is to cut and plant seed tubers on the same day in the Columbia Basin (the soil is rarely wet at planting). No special suberisation operations are performed, planting is from mid March to the end of April. Rotations are variable - winter wheat, corn, alfalfa. Potatoes often follow corn with 3-4 years between crops. Most ground is fumigated before potatoes with

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metham sodium, at $300 US/acre. Methyl Bromide is banned.

Many of the potato enterprises visited used "Dammer-Dyker" equipment - a furrow pitting device used on repellent sands and tight soils with slow infiltration. This reduces run-off water and has aeration benefits.

Variable soil areas are only used for early supply varieties where possible. The worst fields are planted to Shepody, then Ranger Russet, Russet Burbank is planted in the best areas.

Potato production often takes place next to built up areas. Spray operators are reputed to mix odour inhibitors with chemicals to minimise complaints about spraying.

Farm labour costs around $US 4.50/hr, diesel SUS 1.15/US gallon.

A lot of contract work is done, for two reasons - to allow a reduced investment in equipment and to free-up time (a critical issue for large enterprises).

In the USA the growers form groups to negotiate with processing companies and it appears to be a legal practice. Factories are not allowed to collude on price and conditions, however this practice is strongly suspected by growers.

Current processor trend in the USA is for an upper size limit on tubers (16oz) before penalties. This has implications on plant densities.

16.3 Agri Northwest - Colombia Basin

Agri Northwest started as Utah and Idaho sugar. The first potatoes were grown 15 years ago. The company also owned a processing facility and fresh packing shed. The processing factory was sold to Lamb Weston and Agri Northwest now sell potatoes to this company.

The scale of the operation is hard to comprehend. Agri Northwest owns 40,500 ha (100,000 acres) and has 400 employees, growing 5,700 ha (14,000 acres) of centre pivot irrigated potatoes each year. Individual sections are run by managers (15 of) who are ultimately responsible for the crop. Overall management is performed by Mr. Robert Thornton (a son of Dr. Robert Thornton -Pullman University, Washington).

The main line supplying water to the more than 400 centre pivots on the property is 1.2 m in diameter. A team of 5 is permanently employed during crop growth doing nothing but take soil and plant samples for laboratory analysis. The enterprise runs its own research farm and laboratory (with state of the art soil and petiole analysis equipment).

Land costs $US 2 000/acre, SUS 400/acre to lease. Water is not all tied up but environmental movement makes new development difficult. Less than 2% of the total water from the Colombia River goes to agriculture. Agri Northwest uses a 3 yr rotation: 2 yrs maize (11,400 ha (28,000 acres), 1 yr potato. All potato land is fumigated in the autumn with Telone® and Vapam® for nematodes and Verticillium. Maize yield averages 15 USt/ha (6 USt/acre) @ 15.5% moisture. This only pays fixed costs and is not profitable to "stand alone".

Fields are autumn soil sampled and areas as small as 5 acres may have different management strategies for fertiliser. All areas have fertiliser broadcast, some areas also have banded fertiliser. Soil sampling is done weekly for the growing crops to test soil nitrogen. Other nutrients are

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tracked by petiole samples. Soil nitrogen levels are a modified version of Washington State University recommendations.

Phosphorus is applied with irrigation water, as 0:10:34. Mr. Thornton feels that Russet Burbank yield is very sensitive to phosphorus levels, more than any other variety.

Most Agri Northwest pivots are 50 ha (120 acres). There are 140 pivots for potatoes and 280 pivots for maize. Irrigations are scheduled by neutron probe readings and, in normal weather, irrigation is applied every V/i days on the sand. Infra red photos are used every 3 weeks, for irrigation control and late blight detection.

Fumigants applied with irrigation do nothing to control Rhizoctonia. Rhizoctonia can be bad in the Colombia Basin if planting into dry soil (the literature reports problems with wet soil).

Historically there is no irrigation until the plants are well out of the ground, however in dry conditions irrigation is now applied before emergency.

Potatoes average 76 USt/ha (31 USt/acre) over the total area. Of this, 80% of the mid-season Russet Burbank are paid for as # 1 or "useables" by processors, the other 20% are taken by the processors as worthless (no pay). Mid season price in 1993 is expected to be $US 65/US t + incentives and should average $US 80/USt "all up". Washington gross margins are the lowest in the USA. Price can rise to $US 150/USt on the open market in good years, and fall to $US 30/USt in bad years.

Agri North West grows 1,000 acres of Nooksack for french fry processing. Some Nooksack is stored. Shepody and Nooksack yields and even tuber size rely heavily on high plant and stem numbers.

The farm section I visited has 48,000 USt of storage (humidity and temperature control). In total there are 18 x 12,000 USt of controlled potato storage at Agri Northwest (216,000 USt).

Mr. Thornton has to set up (synchronise) 36 x 2 row harvesters at the start of each harvest season. The planters are 6 row and new 3 row harvesters are being bought to match. Harvest started for french fry cultivars on July 19th with Shepody and will finish in the first week of November.

Agri Northwest has 6 transloader operations which allow bulk tubers from the field to be picked over by people on the way to larger trucks. Tubers are transloaded from 10 USt field trucks to 24 USt trucks for long distance transport to the plant. All trucks have self unloading beds - board systems are no good.

Shepody is yielding 32 USt/acre (total) this year. 93% of these are # l's, better than Russet Burbank. Planting distance for Shepody was 9" (same as Nooksack) on 34" rows.

Average seed piece size used by Agri Northwest is: 2.5oz Nooksack, 2.2oz Russet Burbank. The Russet Burbank average seed piece size used to be 1.8 oz, aiming for 2-3 stems in Russet Burbank.

The research farm run by Agri Northwest is 44 acres. There is a greenhouse complex for winter potato research. There is a Research Manager overseeing the work. Next door is a laboratory (large) for soil and petiole analysis.

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In the laboratory, in Atomic Absorption Spectrophotometer is used for K & trace elements. A segmented flow analyser does rapid automatic analysis for N, P, S from petioles and soils. The N is split into nitrate and ammonia forms. The system does 90 samples/hour (700 soils and 200 plant samples per day). Outside entries are charged $27 US for complete petiole analysis or complete soil analysis. $5 US for soil nitrate analysis. The sulfur test in petioles is not much good - the soil test for S is worse.

Agri Northwest is also planting Fuji apples - 1,000 acres per year for each of the next 4 years (just for starters).

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17.0 References collected on tour

Agricultural Experiment Station Oregon State University, Corvallis. (March 1984). "Crop Water Use Curves for Irrigation Scheduling", Special Report 706.

AgriMet. (August 1991). US Bureau of Reclamation, Bonneville Power Administration, Northwest Cooperative Agricultural Weather Network, "Crop Curves".

Barkdoll AW, Davis JR. (February 1992). "Distribution of Colletotnchum coccodes in Idaho and Variation in Pathogenicity on Potato". The American Phytopathological Society (Plant Disease).

Bishop GW, Homan HW, Sandvol LE and Stoltz RL. (September 1982). "Management of Potato Insects In the Western States". A Western Regional Extension Publication (WREP 64).

Callihan RH. (March 1989). "Cultural and Chemical Practices for Commercial Potato Weed Control". Cooperative Extension Service, College of Agriculture, University of Idaho, Bulletin No 695.

Callihan RH and Eberlein CV. "Metribuzin For Weed Control in Potatoes". University of Idaho, College of Agriculture. Current Information Series No 291.

Clough GH. (1992). "Potato Tuber Yield, Mineral Concentration and Quality Following Calcium Fertilization". Production and Culture. Oregon State University.

Davis JR. "Verticillium Wilt of Potato". University of Idaho, College of Agriculture.

Davis JR and Groskopp MD. (1979). "Influences of the Rhizoctonia Disease on Production of the Russet Burbank Potato". American Potato Journal. Vol 56.

Davis JR, Pavek JJ and Corsini DL. (1983). "A Sensitive Method for Quantifying Verticillium dahliae Colonization in Plant Tissue and Evaluating Resistance Among Potato Genotypes". The American Phytopathological Society, Vol 73, No 7.

Davis JR, Sorensen LH, Stark JC and Westermann DT. (1990). "Fertility and Management Practices to Control Verticillium Wilt of the Russet Burbank Potato". American Potato Journal. Vol 67.

Dean BB. (1986). "Seed Quality - Factors Beyond Certification". Proceedings of the 1986 Washington State Potato Conference & Trade Fair.

Dean BB, (1993). "Managing the Potato Production System". Agriculture & Food Science Technology, The Haworth Press, Inc.

Dean BB, Jackowiak N, Nagle M, Pavek J and Corsini D. (1993). "Blackspot Pigment Development of Resistant and Susceptible Solatium Tuberosum L. Genotypes at Harvest and During Storage Measured by Three Methods of Evaluation". American Potato Journal. Vol 70.

Dean BB and Thornton RE. (June 1992). "The Specific Gravity of Potatoes". Issued by

45

Washington State University Coop Extension and US Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914.

Dean BB and Zhicheng Lin. (1991). "Specific Gravity of Potatoes: Old Problem/New Knowledge". Part of the Proceedings of the 1991 Washington State Potato Conference & Trade Fair.

Digital ETgage ™. (1991). Loveland Co. "Measures Evapotranspiration with Proven Accuracy". Manufactured under US Pat. 4,709,585.

Eberlein CV, Haderlie LC, Whitmore JC and Guttieri MJ. (1992 revised). University of Idaho, College of Agriculture. Bulletin No 737.

Eberlein CV and Schaffers WC. "Herbicide Carryover to Potatoes". University of Idaho, College of Agriculture. Current Information Series No 864.

Eldredge EP, Shock CC and Stieber TD. (November-December 1993). "Calibration of Granular Matrix Sensors for Irrigation Management", Agronomy Journal, Vol 85.

Eldredge EP, Mosley AR, Shock CC, Stieber TD and Holmes ZA. "Transitory Water Stress Effects on Potato Tuber Stem End Fry Color". Oregon State University Agricultural Experiment Station Technical Paper Number 0000.

Eldredge et al: "Effects of Transitory Water Stress on Reducing Sugar Levels in Potato Tuber Stem Ends". Oregon State University Agricultural Experiment Station Technical Paper Number 0000.

Haderlie LC, Halderson JL, Corsini DL and Ojala JC. (August 1989 revised). "Potato Vine Killing". University of Idaho, College of Agriculture. Current Information Series No 759.

Hane DC, Mosley AR and Meads CJ. (1991). "1991 Grower-Osu Cooperative Potato Variety Trials". Hermiston Agricultural Research and Extension Center Hermiston, Oregon.

Hane DC and Mosley AR, (1990). "1990 Grower-Osu Cooperative Potato Variety Trials". Hermiston Agricultural Research and Extension Center Hermiston, Oregon.

Hoyman WG, Holland RC. (1974). "Nooksack: A russet Potato Adapted to Northwestern Washington". American Potato Journal. Vol 51.

Johnson G and Johnson O. (1993). "Bruised Seed Piece Trial 1993".

Johnson DA, Miliczky ER. (January 1993). "Effects of Wounding and Wetting Duration on Infection of Potato Foliage by Colletotrichum coccodes". The American Phytopathological Society (Plant Disease).

Johnson DA, Miliczky ER. (1993). "Distribution and Development of Black Dot, Verticillium Wilt, and Powdery Scab on Russet Burbank Potatoes in Washington State". The American Phytopathological Society (Plant Disease). Vol 77, No 1.

Kleinkopf GE, Kleinschmidt GD and Westermann DT. "Tissue Analysis - A Guide to

46

Nitrogen Fertilization for Russet Burbank Potatoes". University of Idaho, College of Agriculture. Current Information Series No 743.

Kleinkopf GE and Westermann DT. (Sept 1987 reprint). "Scheduling Nitrogen Applications for Russet Burbank Potatoes". University of Idaho, College of Agriculture. Current Information Series No 637.

Louisiana Cooperative Extension Service. "Weeds of the Southern United States".

Love SL, Ojala JC, Corsini DL and Pavek JJ. (September 1989). "Potato Variety and Advanced Selection Yield Trials". University of Idaho, College of Agriculture. Bulletin No 706.

Love SL, Pavek JJ, Corsini DL, Whitmore JC and Baker TP. "Cultural Management of Ranger Russet Potatoes". University of Idaho, College of Agriculture. Current Information Series No 919.Malheur County Crop Research Annual Report. (1992). "Special Report 924, June 1993).

McDole RE, Westermann DT, Kleinschmidt GD, Kleinkopf GE and Ojala JC. (1987-91 reprint). "Potatoes". University of Idaho, College of Agriculture. Current Information Series No 261.

McLaughlin JC. "ESP™ K-Sulfate Nutrient Compatibility Tests.

Mojtahedi J, Santo GS and Ingham RE. (1993). "Suppression of Meloidogyne chitwoodi with Sudangrass Cultivars as Green Manure". Journal of Menatology 25 (2):303-311.

Mojtahedi H, Santo GS, Wilson JH and Hang AN. (1993). "Managing Meloidogyne chitwoodi on Potato with Rapeseed as Green Manure". The American Phytopathological Society (Plant Disease) Vol 77, No 1.

Mohan SK, Davis JR, Sorensen LH and Schneider AT. (1992). "Infection of Aerial Parts of Potato Plants by Colletotrichum coccodes and its Effects on Premature Vine Death and Yield". American Potato Journal. Vol 69.

Mohan SK, Hafez SL, Thornton MK and Davis JR. (October 1991). "Powdery Scab of Potato". A Pacific Northwest Extension Publication, PNW 387.

National Potato Anti-Bruise Committee of the Potato Association of America. (1998-92 reprint). "Brusie-Free Potatoes - Our Goal". University of Idaho, C o l l e g e o f Agriculture. Cooperative Extension System Bulletin No 725.

Ojala JC, Love SL, Pavek JJ and Corsini DL. "Potato Varieties for Idaho". University of Idaho, College of Agriculture. Current Information Series No 454.

Ojala JC. Extension Publications Display. (1992). "A listing of Potato and Related Topics Titles".

Oregon Potato Seed Certification Standards. (1993). "Minimum Requirements for Potato Seed Certification in Oregon".

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Oregon State University - Harec Research Plans. (August 1993). "Evaluation of Insecticide for Colorado Potato Beetle, Green Peach Aphid, and Non-Target Pests and Beneficials". Integrated Pest Management Project. (INS92LP).

Oregon State University - Harec Research Plans. (1993). "Utilisation of Transgenic Resistance to Develop Integrated Pest Management Strategies for Potato Insects and Vectored Diseases". Integrated Pest Management Project. (IPM93Btt).

Shock CC, Malheur Experiment Station, Oregon State University, Ontario, Oregon. "Irrigation Management of Potatoes".

Shock et ah "Stem-End Fry Color - French fry, dark-end, potato quality, reflectance, sugar-end, Solatium tuberosum".

Stieber TD and Shock CC. (Sept 2, 1993). "Placement of Soil Moisture Sensors in Sprinkler Irrigated Potatoes". Draft.

Thompson-Johns AL, Love SL. (August 1993). "Tre-State Potato Trials - 1992". University of Idaho.

Thornton RE. (July 14, 1993). "Field Applied Sprout Inhibitors". Pub. Washington State Potato Commission. Spud Topics, A Washington State Industry Report. Vol XXXIX, No 3.

TPS Products Co, Subsidiary of ESCAgenetics Corp. "Description of Proprietary Potato Hybrids".

Ulrich A, Kleinschmidt Dr GD, Sandvol Dr LE. "Potato Field Manual - Nutrient Deficiencies, Diseases and Insect Damage Symptoms". Simplot.

University of Idaho, Cooperative Extension System. (1993) "Proceedings of the Winter Commodity Schools - 1993". Vol 25.

University of Idaho, College of Agriculture. Proceedings of the Winter Commodity Schools -1992. Vol. 24.

University of Idaho College of Agriculture Research and Extension System (Sponsors). (1990). "Proceedings of the University of Idaho Winter Commodity Schools - 1990". Vol 22.

University of Wisconsin - Madison Plant Pathology. (1989). "Preventative Crop and Pest Management Programs for Farming Systems Involving Potatoes".

Washington State University, Cooperative Extension Service, College of Agriculture. (1974). "Reducing Potato Damage During Harvest". Extension Bulletin 646.

Westermann DT. (1993). "Fertility Management". The American Phytopathological Society. Chapter 9.

Western Regional Research Publication Oil. (1992). "Integrated Pest Management for Potatoes in the Western United States". University of California, Division of Agriculture and Natural Resources Publication Oil.

Western Regional Potato Variety Trial Report. (1992). "State Experiment Stations and USDA-ARS Cooperating".

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18.0 Itinerary

Aug. 7 Arrive, USA

Aug. 8-12 Madison (Wisconsin)

Aug. 13 Travel

Aug. 14-16 Corvallis (Oregon) Oregon State Univ.

Aug. 17 Travel

Aug. 18 Hermiston Ag. Res. Stn. Oregon State Univ.

Aug. 19-23 Pasco (Washington)

Prosser Res. Stn. Washington State Univ.

Potato Association of America Conference

Dr. A. Mosely (Alvin), soil and irrigation management, improved varieties, nutrition. Dr. M. Powelson (Mary), potato plant pathology, Verticillium early dying syndrome.

Dr. G. Reed (Gerry), nematode and insect control. Dr. G. Clough (George), irrigation of sandy soils, groundwater quality, plant nutrition. Mr. D. Hane (Dan), variety development.

Mr. R. McCary (Roger), Mr. M. Stephenson (Mike), Consultants to Potato Industry, neutron probe, petiole analysis, aerial photos.

Dr. J. Santo (Jerry), Dr. H. Mojtahedi (Hassan), nematode research. Dr. W. Dean (Bill), bruising, plant physiology, environmental stress. Dr. D. Johnson (Dennis), potato plant pathology, black dot.

Aug. 24 Travel

Aug. 25-26 Othello (Washington)

Othello Ag. Res. Stn. Washington State Univ.

Aug. 27 Ontario (Oregon) Malheur Res. Stn.

Mr. J. Shields (John) - McCain Foods, potato processing plant.

Dr. R. Thornton (Bob), Mr. S. Holland (Steve), improved varieties, tuber disorders, environmental stress, potato crop establishment.

Dr. C. Shock (Clint), potato nutrition, irrigation, tuber disorders.

Aug. 28-29 Travel

Aug. 30 Kimberley Res. Stn. University of Idaho

Dr. G. Kleinkopf (Gale), potato plant nutrition, tuber disorders, potato crop establishment, potato storage. Dr. D. Westermann (Dale), potato plant nutrition. Mr. M. Lewis (Mike), potato storage.

Travel

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Sept. 1-2

Sept. 3

Aberdeen (Idaho) Aberdeen Res. Stn.

Idaho Falls (Idaho) Idaho State Univ. Res. Stn

Dr. J Pavek (Joe), Dr. S. Love (Steve), potato breeding and cultivar development. Dr. D. Corsini (Dennis), potato plant pathology/new cultivars. Dr. J. Davis (Jim), potato plant pathology. Dr. J. Stark (Jeff), irrigation and soil management. Dr. L. Sandvol (Larry), potato insects.

Dr. J. Ojala extension.

(John), potato agronomy and

Sept. 4-5 Travel

Sept. 6 Spokane (Washington) Airport, fly to Australia

19.0 Finance

Funds for this study tour was provided by contributions from McCain Foods ($2 500), Potato Growers' Association of South East South Australia ($1 500), Horticultural Management ($930) and the Department of Primary Industries (Agriculture) Overseas Visit Line ($4 000).

Costs

Travel

Economy airfares :

Car hire & fuel

Accommodation

Accommodation and living expenses

Adelaide-Sydney-Chicago-Madison-Portland-Spokane-Vancouver-Sydney-Adelaide 25 days

$ 2 861 $ 1 500

30 days accommodation @ $125/day Conference registration Insurance ($179), passport ($80) Sundries - Publications, film

TOTAL

$ : 5 750 $ 400 $ 269 $ 150

$ 8 930

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