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SID 5 Research Project Final Report

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NoteIn line with the Freedom of Information Act 2000, Defra aims to place the results of its completed research projects in the public domain wherever possible. The SID 5 (Research Project Final Report) is designed to capture the information on the results and outputs of Defra-funded research in a format that is easily publishable through the Defra website. A SID 5 must be completed for all projects.

This form is in Word format and the boxes may be expanded or reduced, as appropriate.

ACCESS TO INFORMATIONThe information collected on this form will be stored electronically and may be sent to any part of Defra, or to individual researchers or organisations outside Defra for the purposes of reviewing the project. Defra may also disclose the information to any outside organisation acting as an agent authorised by Defra to process final research reports on its behalf. Defra intends to publish this form on its website, unless there are strong reasons not to, which fully comply with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.Defra may be required to release information, including personal data and commercial information, on request under the Environmental Information Regulations or the Freedom of Information Act 2000. However, Defra will not permit any unwarranted breach of confidentiality or act in contravention of its obligations under the Data Protection Act 1998. Defra or its appointed agents may use the name, address or other details on your form to contact you in connection with occasional customer research aimed at improving the processes through which Defra works with its contractors.

Project identification

1. Defra Project code HH3118TPC

2. Project title

Protected herbs: Best practice guidelines for integrated pest and disease management

3. Contractororganisation(s)

ADAS BoxworthBoxworthCambridgeCB3 8NN

54. Total Defra project costs £ 90,002(agreed fixed price)

5. Project: start date................ 01 October 2003

end date................. 30 September 2006

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6. It is Defra’s intention to publish this form. Please confirm your agreement to do so...................................................................................YES NO (a) When preparing SID 5s contractors should bear in mind that Defra intends that they be made public. They

should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow.Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the SID 5 can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer.In all cases, reasons for withholding information must be fully in line with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.

(b) If you have answered NO, please explain why the Final report should not be released into public domain

Executive Summary7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the

intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work.The UK protected herb industry is diverse, including all year round (AYR) glasshouse production of pot herbs for supermarkets, seasonal production of pot or cut herbs in unheated structures for garden centre sales and culinary use, and glasshouse propagation of both culinary and pharmaceutical herbs for field planting. These crops are damaged by a wide range of pests and diseases. Use of pesticides on herbs is much more restricted than on other protected crops. These restrictions, together with pesticide resistance problems with some pests and diseases, and with increasing retail demands for reduced pesticide use, mean that many growers use non-chemical control methods wherever possible. Integrated Crop Management (ICM) is now used on an increasing number of herb nurseries, combining cultural and biological control methods with minimal use of compatible pesticides. Retailers also demand high quality produce, with ‘zero tolerance’ of pests and diseases. Thus ICM methods need to be highly effective and development of suitable ICM control strategies is needed for some pests and diseases.

This project, funded by both Defra and the Horticultural Development Council (HDC, project PC 210) aimed to: Collate information on existing knowledge of ICM methods in both herbs and other protected crops. Test alternative strategies for controlling selected pests and diseases where there are no existing

effective solutions for use in ICM. Provide growers with Best Practice Guidelines for ICM. Communicate the Best Practice Guidelines to the industry.

Information was collated and evaluated to identify control options for selected priority pests and diseases of the most widely grown protected herbs. Information used for formulating the Best Practice Guidelines was collated from ADAS research and consultancy experience, from UK and international scientific and industry contacts, and the scientific literature including reports from HDC, Defra and the internet. In addition, visits to seven nurseries representing different sectors of the protected herb industry (propagator, Experimental work focussed on priority pest and disease problems for which ICM-compatible management options are available on other crops, but that have not been validated for use on protected herbs. Options for the control of shore flies (on mint), leafhoppers (on mint and sage), powdery mildew (on parsley and apple mint) and pythium root rot (on coriander) were evaluated.

An experiment on potted mint on a commercial herb nursery evaluated biological control agents against shore flies, as individual and combined treatments. None of the individual treatments (the predatory beetle Atheta coriaria, the predatory mite Hypoaspis aculeifer and the insect-pathogenic nematode Steinernema feltiae) reduced shore fly numbers at the end of the 5 week cropping period. The combination of the three biological control agents significantly reduced numbers of shore flies (a mean of

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0.4 per pot, compared with a mean of 2.3 per pot in untreated controls). However, it is possible that the naturally-occurring shore fly parasitoid, Aphaereta debilitata contributed to shore fly control. Large numbers of this natural parasitoid were found on the nursery and its potential role in ICM programmes needs to be determined.

A glasshouse experiment was done to evaluate the control of the ‘sage’ leafhopper, Eupteryx melissae by weekly releases of the egg parasitoid, Anagrus atomus to apple mint and sage plants in replicate insect-proof mesh cages. Four weeks after adult leafhopper release, significantly fewer nymphs per plant (a mean of 11.8) were found in cages where Anagrus had been released than in control cages (a mean of 54.2 per plant). In laboratory tests to evaluate the potential control of ‘sage’ leafhopper nymphs by the insect-pathogenic nematode Steinernema feltiae (‘Nemasys F’), a mean of 65% of the leafhopper nymphs were dead two days after spraying infested leaves with nematodes, compared with 5% dead on leaves sprayed with water. In a small-scale glasshouse experiment with infested sage plants, the nematodes gave no control of leafhopper nymphs two days after treatment. This lack of control is likely to have been due to difficulties in targeting leafhopper nymphs on leaf undersides, and to the hot, dry conditions in the glasshouse, causing the nematodes to desiccate shortly after application. In laboratory tests, the predatory bug Anthocoris nemoralis did not feed on leafhopper nymphs or adults on infested sage leaves over a 24-hour period.

Alternatives to conventional fungicides were identified for powdery mildew control on protected herbs. Even under high disease pressure, weekly sprays of 0.25% potassium bicarbonate (food-grade) + wetter, K50 (50% potassium bicarbonate; 3 L product/ha) + wetter, or 0.15% Milsana® (giant knotweed extract) + wetter, reduced percentage leaf area affected on apple mint, from 25% in the untreated control to less than 3%. Rapid disease development once the spray programme was complete demonstrated that regular sprays with such products are required to maintain effective powdery mildew control.

The following treatments as compost amendments were evaluated for their effects on coriander root rot (Pythium sp.) in an inoculated pot experiment: Gliomix, Stimagro, Agralan Revive, Polyversum®, Trianum-G, chitin and an experimental product. Percentage germination was reduced in all of the inoculated treatments compared with the inoculated control, due to infection by Pythium sp. None of the amendment treatments significantly reduced coriander root rot compared with the inoculated control. Lack of disease control can be partly attributed to high inoculum pressure.

During the project, information on integrated pest and disease control on protected herbs has been formulated and delivered to the industry in a range of formats including a booklet of Best Practice Guidelines to be published by HDC. The project website (www.protectedherbs.org.uk) provides an aid to the identification of common pests and disease of herbs as well as project summary information. Workshops organised in conjunction with HDC were held at three venues in September 2006 providing training for 46 members of the protected herb industry in integrated pest and disease management. In addition, the project has generated 5 publications in the trade press, 14 presentations at conferences and growers’ events, and advice to individual growers.

The project has highlighted several opportunities for further work on integrated management of pests and diseases on protected herbs. For example, building on the results of year 1 research on biological control of shore flies, an HDC-funded ADAS-led project started in 2005. The project (PC 239) is entitled ‘Protected herbs, ornamentals and celery: development of an on-nursery rearing system for Atheta coriaria for reduced cost biological control of sciarid and shore flies’.

Project Report to Defra8. As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with

details of the outputs of the research project for internal purposes; to meet the terms of the contract; and to allow Defra to publish details of the outputs to meet Environmental Information Regulation or Freedom of Information obligations. This short report to Defra does not preclude contractors from also seeking to publish a full, formal scientific report/paper in an appropriate scientific or other journal/publication. Indeed, Defra actively encourages such publications as part of the contract terms. The report to Defra should include: the scientific objectives as set out in the contract; the extent to which the objectives set out in the contract have been met; details of methods used and the results obtained, including statistical analysis (if appropriate); a discussion of the results and their reliability; the main implications of the findings;

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http://www.protectedherbs.org.uk/

possible future work; and any action resulting from the research (e.g. IP, Knowledge Transfer).

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1. INTRODUCTION

This project, funded by both Defra and the Horticultural Development Council (HDC, project PC 210), aimed to provide integrated solutions for pest and disease control in protected herbs. This was done through the dissemination of appropriate information available from current strategies used on both protected herbs and other protected cropping systems, and from project experiments evaluating alternative options for the control of priority pests and diseases for which there is no existing effective integrated solution. The project addressed Defra’s policy objectives of minimising pesticide usage and promoting sustainable, adaptable and cost-effective production methods, which meet consumer requirements for a safe food supply chain and environmentally-responsible growing systems.

2. OBJECTIVE 1: to collate and evaluate currently available information on potential integrated management solutions for priority pest and disease problems on protected herbs.

Status: Complete

The importance of different pests and diseases on protected herbs varies according to herb crops cultivated and production system used. The priority pest and disease problems to be included in the Best Practice Guidelines (summarised in Tables 1 and 2) were selected after consultation with the project steering committee (which included industry representatives).

Table 1. Priority pests on protected herbs

Pest Crops affected Production systemHigh priority1. Shore fly (Scatella tenuicosta) Feed on algae on compost

of slower-growing spp. e.g. basil and mint

Pot herbs and in propagation

2. ‘Sage’ leafhopper (Eupteryx mellisae)

Wide host range e.g. basil, marjoram, mint, rosemary, sage, thyme

Pot and cut herbs, particularly where stock plants are kept

3. Glasshouse whitefly (Trialeurodes vaporariorum) and the quarantine pest, tobacco whitefly (Bemisia tabaci)

Wide host range e.g. basil, mint, sage.

Risk of B. tabaci on imported cuttings and plants.

Mainly pot herbs but can also be a problem on overwintered parsley and coriander grown for cutting.

4. Aphids (various spp.). Problem species are peach-potato aphid on basil, and those not susceptible to parasitoids used in IPM e.g. willow-carrot aphid, hawthorn-parsley aphid, mint aphid and shallot aphid.

Wide host range. All

Moderate priority5. Thrips, particularly western flowerthrips ( Frankliniella occidentalis)but Thrips tabaci also occurs.

Mainly basil, chives, parsley

All

6. Caterpillars (various spp.) Mainly basil, mint, thyme All7. Leaf miners (Chromatomyia and Liriomyza spp. including the quarantine pest, South American leaf miner, Liriomyza huidobrensis).

Basil, mint, other labiates.Risk of L. huidobrensis on imported cuttings and plants.

All

8. Sciarid fly (Bradysia difformis) Wide host range, favours parsley

Pot herbs and in propagation, particularly in organic composts

Lower priority9. Two-spotted spider mite (Tetranychus urticae)

Lemon balm & verbena, mint, tarragon

All

10. Vine weevil (Otiorhynchus sulcatus)

Wide host range Potted stock plants, particularly where ornamentals e.g. alpines also grown.

11. Slugs and snails (various spp.) Wide host range All12. Moth flies (Psychodidae) Detritus feeders in wet

situationsPot herbs, particularly in ebb and flood / hydroponic systems

13. Flea beetles (various spp.) Rocket, mustards, sorrel Cut herbs

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Table 2. Priority diseases on protected herbs

Disease Crops affected Production systemHigh priority1. Damping off diseases (e.g. Pythium, Phytophthora and Rhizoctonia)

Wide host range for Pythium

Phytophthora e.g. on parsley

Rhizoctonia e.g. on lavender and thyme at propagation, and chamomile.

Pot and soil grown Pythium and Phytophthora

spp. may thrive in re-circulating irrigation systems

2. Powdery mildews E.g. mint, sage, parsley, some varieties of rosemary, and dill.

All year round (AYR) production

Pots under glass/polythene3. Rusts E.g. mint, thyme, marjoram,

chives and tarragonAll, but less of a problem than on field crops

5. Grey mould (Botrytis cinerea) Wide host range, e.g. basil, dill and oregano

All, but sporadic. Most common on multi-cut herbs.

4. Leaf spots (e.g. Septoria, Ramularia and Colletotrichum)

Septoria on parsley Ramularia on coriander Colletotrichum on St

John’s wort and basil

All but sporadic

Moderate priority6. Downy mildews E.g. chives (mainly

outdoor), sage and dill Pots under glass/polythene

7. Vascular wilts (e.g. Fusarium and Verticillium)

E.g. basil and parsley Cut herbs. Sporadic but can be severe, e.g. after multiple cuttings of basil

Lower priority8 Sclerotinia and Sclerotium cepivorum

Sclerotinia rot e.g. on basil, coriander, fennel

S. cepivorum causing white rot on chives

Soil grown and occasionally in pot herbs

9 Bacterial blight (Pseudomonas sp.) Coriander Rarely a problem; more problematic on field herbs

10 Viruses e.g. on Umbelliferae Rarely a problem

Information was collated and evaluated to identify control options for the selected priority pests and diseases of the most widely grown protected herbs. This process was ongoing for the duration of the project to ensure that the most up-to-date information could be made available to the industry. Information used for formulating the Best Practice Guidelines was collated from ADAS research and consultancy experience, from UK and international scientific and industry contacts, and the scientific literature including reports from HDC and Defra-funded research and the Internet. In addition, visits to seven nurseries representing different sectors of the protected herb industry (propagator, cut herbs, pot herbs and all year round (AYR) production) provided key information on pest and disease problems experienced and management strategies currently used. Grey mould (Botrytis cinerea) on basil, mint rust and powdery mildew on parsley and mint, were the most common diseases occurring across a range of production systems and strategies for control varied between nurseries. The main pest problems were shore flies and aphids on AYR pot herbs, leafhoppers, thrips, whitefly and caterpillars on seasonal pot herbs, and leafhoppers, thrips and flea beetles on cut herbs.

3. OBJECTIVE 2: to evaluate control strategies for selected pest and disease problems using representative host plant species and production systems.

Status: Complete

For certain priority pest and disease problems, alternative management options are available but have not been validated for use on protected herbs. Following discussion at the first steering group meeting (December 2003), experimental work in project year 1 focussed on evaluating options for the control of shore flies and powdery mildew. Following discussion at the second steering group meeting (November 2004), experimental work in project year 2 focussed on evaluating options for the control of powdery mildew (on mint), pythium root rot (on coriander) and leafhoppers (on mint and sage).

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3.1. Shore flies

3.1.1. IntroductionShore fly, Scatella tenuicosta, is a major pest on pot herbs and on those in propagation. Shore flies feed on algae rather than on the herbs, but cause contaminant problems through presence of adult flies or faecal droppings, particularly on slower-growing herbs such as basil, mint and thyme. The flies are also potential carriers of diseases e.g. Pythium and Thielaviopsis. There is no available effective pesticide for the control of shore flies on herbs or other protected crops. The predatory mites, Hypoaspis miles and Hypoaspis aculeifer and the entomopathogenic nematodes, Steinernema feltiae (both recommended for the control of sciarid flies) are sometimes used by growers against shore flies, but with little success. The predatory rove beetle, Atheta coriaria has recently become available for biological control of both sciarid and shore flies. Initial research on the potential of the A. coriaria was done in Canada (Carney et al., 2002). Experimental use on several UK nurseries growing ornamentals has indicated that A. coriaria can give a useful reduction in numbers of both sciarid and shore flies.

An experiment was done in this project to evaluate A. coriaria, H. aculeifer and S. feltiae as individual and combined treatments, against shore flies on potted mint on a commercial nursery.

3.1.2. Methods

The experiment was done on a pot herb nursery in May and June 2004. The experimental plants were potted mint, from sowing to marketing (4-week production time). Eight 10 m2 ‘ebb and flood’ benches were used for the experiment, one bench per treatment. One third of each bench as filled with un-spaced pots sown with mint seeds. This area of bench was divided into three replicate plots, each 1m2. There were 132 pots in each plot (22 rows of six pots). The three plots on each bench were covered with insect-proof netting, secured with bulldog clips around the edge of the bench. As per commercial practice on the nursery, the pots were spaced with an automatic spacing machine, 18 days after sowing. The insect-proof netting on each bench was removed for this purpose, but was replaced immediately afterwards on benches used for all treatments except for treatment 1 (see Table 3). After spacing, each plot still occupied 1m2 but there were only 44 pots rather than the 132 pots before spacing. The pots remained on the benches for a further 8-10 days before they reached the marketing stage.

Shore fly adults were collected from the nursery and released to each bench under the net covers on three occasions, to mimic the continued natural immigration of flies. On days 6 and 11, 20 shore flies per plot were released and on day 18, five flies per plot were released after spacing.

The treatments applied to each respective bench are shown in Table 3. Treatment 1 represented the shore fly control strategy used by the host grower at the time of the experiment. The grower used horticultural fleece over the pots for the first 18 days, as a cultural control method to reduce the numbers of shore fly adults laying eggs on the compost in the pots. This fleece was removed at spacing on day 18 and not replaced. On the experimental benches, insect-proof netting was used rather than fleece as this was more effective as a fly barrier. The insect-proof netting was replaced after spacing on benches used for treatments 2-8, as this reduced the risk of migration of A. coriaria and H. aculeifer between the different treatments. However, the netting was not replaced after spacing on the bench used for treatment 1, as this tested the efficacy of the grower’s strategy, and also allowed the monitoring of any naturally-occurring shore fly predators or parasitoids on the ‘open’ pots.

Fifteen pots per bench (five per plot) were removed on day 6 before the first treatments were applied and again on day 18 just before spacing and before further treatments were applied. A final 15 pots per bench were removed on day 28, just before the marketing stage. Each sampled pot was placed into an individual larger pot, covered with insect-proof netting. The pots were kept in a controlled temperature room for 16 days at 20 C, to allow any shore fly adults to develop from eggs, larvae or pupae that were present in the compost at sampling. A small yellow sticky trap was secured on the inside of each ‘emergence’ pot and numbers of shore fly adults per sticky trap were recorded. On day 16, the pots were frozen and any emerged flies which were not yet caught on the traps were washed off the surface of the frozen compost. Total numbers of shore flies per pot (from the sticky trap and frozen compost) were recorded. The data was analysed using analysis of variance (ANOVA).

Compost temperatures were monitored during the experimental period, using two Tiny Talk data loggers, buried in the compost in extra pots on two of the experimental benches.

Table 3. Biological control treatments tested for control of shore flies on potted mint (day number is days after sowing); * = grower’s own strategy in the rest of the glasshouse.

Treatment Biological control Application rate Timing Mesh covers removed at

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agent spacing on day 18

1. * Hypoaspis aculeifer

Atheta coriaria adults

Steinernema feltiae(‘Nemasys F’)

500 per m2

17 per m2 on day 6 (equivalent to 6 per m2

at spacing) and 2 per m2 at spacing (equiv. To 6 per m2 on unspaced pots) on day 18

1 million per m2

Day 6

Day 6

Day 18

Days 6, 11 and 18

Yes

2. As in treatment 1 As in treatment 1 As in treatment 1 No3. Atheta coriaria adults 17 per m2 on day 6

(equiv. to 6 per m2 at spacing) and 2 per m2

on day 18

Day 6

Day 18

No

4. Atheta coriaria mixed life stages

23 per m Day 6 No

5. Hypoaspis aculeifer 500 per m2 Day 6 No

6. Steinernema feltiae 1 million per m2 Days 6, 11 and 18 No7. Steinernema feltiae 2.5 million per m2 Days 6 and 18 No

8. Untreated control - - No

3.1.3. Results

No shore flies were recorded in pots sampled on day 6. On day 18, there was a mean of 39 shore flies per untreated pot and none of the treatments had reduced numbers of shore flies at that stage. The data for numbers of shore flies per plot on day 28 were transformed before analysis. The log 10 mean numbers of shore flies per plot, and the back-transformed mean numbers per individual pot are given in Table 4. Mean numbers of shore flies per untreated pot were 2.3 and only treatment 1 had significantly reduced (P<0.05) numbers of shore flies, to 0.4 per pot (Table 4).

Mean compost temperatures during the experimental period were 22-27C and maximum compost temperatures were 26-41C (Figure 1).

Table 4. Log10 mean numbers of shore fly adults per plot at marketing (back-transformed means perindividual mint pot in parentheses). * = significantly lower numbers than in untreated controls (P<0.05).

Treatment Log10 mean number of shore flies per plot

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1. A. coriaria, H. aculeifer & S. feltiae, mesh bench covers removed at spacing

0.46* (0.38)

2. A. coriaria, H. aculeifer & S. feltiae, mesh bench covers replaced at spacing

1.183 (2.85)

3. A. coriaria adults 1.071 (2.16)

4. A. coriaria mixed life stages 0.966 (1.65)5. H. aculeifer 1.246 (3.32)

6. S. feltiae x 3 1.199 (2.96)

7. S. feltiae x 2 1.515 (6.35)

8. Untreated control 1.094 (2.28)

0

5

10

15

20

25

30

35

40

45

14/05/04 22/05/04 30/05/04 07/06/04

Tem

pera

ture

deg

C

24 hour meanDaily max

Figure 1. Mean and maximum compost temperatures during shore fly experiment.

3.1.4. Discussion

The results indicated that none of the individual biological control agents reduced numbers of shore flies. The results with S. feltiae and H. aculeifer were consistent with those of Finnish researchers, who reported that higher application rates than those used in this experiment were needed for effective shore fly control on mint, i.e. two applications of S. feltiae at 5 million per m2 and one application of H. aculeifer at 5,000 per m2 (Vanninen & Koskula, 2003 and 2004 respectively). However, these effective rates are too expensive for commercial use in both Finland and the UK. The rates of the biological control agents used in this experiment were the same as those used by the host grower.

Mean numbers of shore flies per pot were much lower on day 28 than on day 18. This result is typical of shore fly populations on herbs, due to the algal growth on the surface of the compost being inhibited by reduced light as the plant canopy covers the pots. The combination of the three biological control agents gave a significant reduction in shore fly numbers on plants on day 28 at the marketing stage, but only in Treatment 1, where the insect-proof netting was removed on day 18. No reduction in shore flies was given in Treatment 2, where the same combination of biological control agents was used, but the netting was replaced for the final 10 days of

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production, to prevent migration of predators between treatments. Large numbers of the natural shore fly parasitoid, Aphaereta debilitata were found outside the experimental plots on the host nursery during the experiment period. A. debilitata adults were recorded on the sticky traps in the emergence pots from treatment 1, thus it is likely that that removing the netting on day 18 allowed them access to the pots and that they contributed to shore fly control. Subsequent HDC-funded research in project PC239 on a different pot herb nursery showed that an exceptionally high natural population of A. debilitata led to up to 99% parasitism of shore flies on mint at the marketing stage (Bennison, 2007).

Temperature data indicated that although mean compost temperatures (22-27 C) were within the effective range of the three biological control agents tested, maximum temperatures exceeded their upper limits for most of the experimental period (over 30C and 32C on 23 and 18 days respectively). The upper temperature limit for S. feltiae is 30C (Becker Underwood technical information), that of A. coriaria is 32C (Miller & Williams, 1983) and that of H. aculeifer is likely to be 32C, which is the upper limit for a related species, H. miles (Malais & Ravensberg, 1992). However, it is possible that the compost temperatures recorded by the data loggers were higher than compost temperatures in the mint pots, as the loggers were placed in pots of compost but did not have mint plants in the compost to provide shade.

The lack of control by A. coriaria adults or mixed life stages could also have been due to insufficient prey being available when the predators were released on day 6, together with adult shore flies. Experience on the nursery had indicated that ‘natural’ shore flies would have laid eggs on the pots before they were covered with netting on day 6, thus providing prey for the A. coriaria as soon as they were released. However, the pots removed on day 6 were shown to have no natural shore fly infestation. Thus the voracious A. coriaria may have had insufficient prey to establish, before offspring of the released adult shore flies were available as prey.

3.2. Leaf hoppers

3.2.1. IntroductionLeafhoppers are a persistent problem on many herb species e.g. basil, marjoram, mint, sage and thyme. The main species damaging herbs is the chrysanthemum or ‘sage’ leafhopper, Eupteryx melissae. Plant losses due to damage can be significant and additional labour costs are incurred through applying frequent pesticides and picking off damaged leaves. Since the revocation of heptenophos in April 2001, there has been no effective control measure available for use on herbs against leafhoppers. Pyrethroid pesticides and various plant extract products give poor control and pyrethroids are incompatible with biological control agents. Pymetrozine (Chess) has specific off-label approval for use against aphids on protected herbs and will give some control of leafhoppers and is compatible with IPM, but its 14-day harvest interval is impractical on short-term herb crops. The leafhopper egg parasitoid, Anagrus atomus is available for the control of glasshouse leafhopper, Hauptidia maroccana e.g. on tomatoes, but is reported by the supplier to be ineffective against E. melissae. However, ADAS research in HDC-funded project PC178 showed that naturally-occurring A. atomus were present on E. melissae on several herb nurseries using IPM (Bennison, 2001). The entomopathogenic nematode Steinernema feltiae is now used commercially as foliar sprays for the control of thrips, and may have potential against leafhoppers, although they have not been tested to date against this pest. The generalist predatory bugs, Anthocoris spp. may also have potential for control of leafhoppers and Anthocoris nemoralis has recently become available for use on pear against psyllids.

Three experiments were done in this project to test potential biological control agents against E. melissae on herbs:

Experiment 1 tested the leafhopper egg parasitoid Anagrus atomus. Experiment 2 tested the entomopathogenic nematodes Steinernema feltiae.Experiment 3 tested the predatory bugs Anthocoris nemoralis.

3.2.2. Methods

Experiment 1The experiment was done in a research glasshouse at ADAS Boxworth in September and October 2005. Eight insect-proof mesh cages were used for the experiment, four replicate cages for each of two treatments. One mint and one sage plant was placed in each cage and 20 E. melissae adults were released to each cage. Anagrus atomus were released to four of the cages (25 per cage) the day after leafhopper release and on three further weekly occasions. The remaining four cages acted as untreated controls. Four weeks after leafhopper adult release, the plants were destructively assessed for numbers of live E. melissae nymphs. The data for the mint and sage plant in each cage were combined and analysed using analysis of variance (ANOVA).

Experiment 2

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An initial leaf bioassay was done to test the susceptibility of E. melissae nymphs to S. feltiae. Leaves infested with leafhopper nymphs were detached from sage plants in the E. melissae culture at ADAS Boxworth. Using methods developed for testing the nematodes against thrips in Defra-funded project HH3102TPC (Bennison, 2006), three leaves were sprayed with S. feltiae (‘Nemasys F’) and three were sprayed with water as controls. S. feltiae were applied at twice the rate recommended for thrips control, i.e. at 500,000 per 1000m2 in 100 L of water (equivalent to 50 nematodes per cm2). The leaf petioles were stuck into wetted cubes of ‘oasis’ and placed into individual sealed jars and incubated at 21C for two days. After two days, the number of live and dead leafhopper nymphs were recorded. Ten of the dead nymphs were washed in water and then dissected in a droplet of clean water and the presence of any nematodes was recorded. Total numbers of live and dead leafhopper nymphs on the three leaves per treatment were compared using chi-square analysis.

Following the leaf bioassay, a small-scale glasshouse experiment was done at ADAS Boxworth. Six sage plants infested with E. melissae were used for the experiment, two replicate plants for each of three treatments. The treatments were S. feltiae at the recommended and twice the recommended rate for thrips control, and water as a control. A wetter (Agral) was added at a 0.04% concentration to all treatments. Numbers of live and dead leafhopper nymphs were counted on six marked leaves just before and three days after treatment.

Experiment 3A laboratory bioassay was done to determine whether Anthocoris nemoralis will predate on E. melissae. Five replicate sage leaves were detached from sage plants infested with E. melissae nymphs. Leaves with equal numbers of leafhopper nymphs were selected. The leaf petioles were stuck into wetted cubes of ‘oasis’ and were placed into individual screw-top tubes, provided with ventilation holes covered with insect-proof mesh. One A. nemoralis adult female was added to each tube. The tubes were incubated at 21C with an 18:6 light:dark period for 24 hours. Numbers of leafhopper nymphs and adults per leaf were recorded before placing into the tubes and 24 hours later.

3.2.3. Results

Experiment 1Four weeks after leafhopper adult release, there were significantly (P<0.05) fewer (11.8) mean leafhopper nymphs per plant in cages treated with weekly releases of Anagrus atomus than in untreated cages (54.2).

Experiment 2In the leaf bioassay, two days after treatment, there was a significantly (P<0.001) higher proportion of dead leafhopper nymphs (65%) on leaves sprayed with S. feltiae than on leaves sprayed with water (5%). Nematodes were found in seven of the 10 dissected leafhopper cadavers, with 1-6 nematodes being recorded in each cadaver. Cadavers with nematodes were green with a reddish-brown head or rear end of the body, whereas live nymphs and those without nematodes were green. In the glasshouse experiment, no dead leafhopper nymphs were recorded on leaves treated with either rate of S. feltiae or with water. There was a mean of four live leafhopper nymphs per leaf on water-treated plants and numbers were not reduced on nematode-treated plants.

Experiment 3There were 15 leafhoppers on each of the five leaves before and 24 hours after the A. nemoralis were added. The leafhoppers were all at the nymphal stage before the predators were added and some had developed into adult leafhoppers 24 hours later.

3.2.4. Discussion

Experiment 1The results demonstrated that Eupteryx melissae eggs are susceptible to the egg parasitoid Anagrus atomus. Unlike the eggs of the glasshouse leafhopper, Hauptidia maroccana which turn red when parasitised, those of E. melissae turn brown and as they are laid deeper in the leaf veins than those of H. maroccana, they are much more difficult to recognise, even using a microscope. This distinguishing feature of parasitised E. melissae eggs was not known prior to this research, which explains why parasitism of this leafhopper species had been previously unrecorded. A. atomus was demonstrated to have the potential for control of E. melissae and further work will be necessary to determine effective release rates and timings.

Experiment 2The results of the leaf bioassay gave the first reported record of S. feltiae killing leafhoppers and the nematodes were demonstrated to have potential as a biological control agent for E. melissae. However, the experimental conditions offered ideal conditions for the nematodes, i.e. a suitable temperature and high humidity in the sealed jars, which will have maintained leaf wetness throughout the 2-day period. The lack of control by S. feltiae in the glasshouse experiment could have been due to the very hot, dry conditions in the glasshouse during the experiment, which will have caused the leafhoppers to desiccate shortly after application. Work in Defra-funded

SID 5 (Rev. 3/06) of 26

project HH3102TPC showed that S. feltiae survived on chrysanthemum leaves for only 2-3 hours after application in glasshouses, even when applied just before black-out, which would extend the period of leaf wetness (Bennison, 2006). Further work is required to determine methods for effective application of nematodes to herbs for the control of leafhoppers, particularly as S. feltiae is already used as a drench on herbs for the control of sciarid flies.

Experiment 3The results indicated that Anthocoris nemoralis do not predate on E. melissae nymphs. This result was surprising, as Anthocorid bugs are generalist predators, and a related species, A. nemorum has been reared on leafhoppers (Herard & Chen, 1985). In HDC-funded project PC178, Anthocoris nemorum was found occurring naturally on several herb nurseries using IPM, on leafhopper-infested plants. However, A. nemorum is difficult to rear and is not commercially available.

3.3. Evaluation of alternative products for the control of powdery mildew

3.3.1. IntroductionPowdery mildews affect a wide range of herb hosts including members of the Labiatae (e.g. sage, thyme and rosemary), Umbelliferae (e.g. parsley, coriander and dill), and Compositae (e.g. tarragon). Symptoms affect plant appearance, reduce plant vigour and also reduce essential oil yield. While high relative humidity is required for infection to occur, disease spread is most prevalent during warm, dry conditions. Sulphur (Thiovit Jet) and azoxystrobin (Amistar) both have specific off-label approvals (SOLAs) for treatment of powdery mildew on herbs but are rarely used by protected herb growers. Sulphur can disrupt IPM as it is harmful to certain biological control agents, e.g. the predatory midge Aphidoletes aphidimyza, which is widely used for aphid control, particularly on parsley. A range of other products has been reported in scientific literature as having activity against powdery mildews.

In experiment 1, the objective was to determine the efficacy of single products for the control of powdery mildew on two susceptible herb crop species, apple mint (Mentha suaveolens) and parsley (Petroselinum crispum). Based on the results of experiment 1, the objective in experiment 2 was to evaluate the efficacy of programmes of alternating products for longer-term control of powdery mildew on apple mint.

3.3.2. Methods

Experiment 1The experiment was sited in two glasshouse compartments at ADAS Arthur Rickwood, Cambridgeshire in October 2004. Apple mint was supplied as plugs of rooted cuttings from a commercial pot herb nursery and was used 4 weeks after rooting. Because of the high risk of powdery mildew at the nursery, plug plants were treated with 2% potassium bicarbonate by the grower 2 weeks prior to trial commencement. The individual plugs were transferred to F1 compost in 9 cm diameter pots (one plant per pot) and placed in trays in a glasshouse (12-15oC, ambient light). Pots of germinating parsley were supplied from an AYR pot herb nursery. They were placed in a separate glasshouse compartment (16-17oC, ambient light).

Table 5. Products tested for control of powdery mildews on apple mint and parsley

Treatment Application rate* Timing**1 Untreated control - -2 Amistar (azoxystrobin) 1 L/ha (1 ml/1 L water) Day 03 Thiovit Jet (sulphur) 0.01 Kg/5 L water (2 g/1 L water) Day 0 and 74 Experimental product (NF 149) 0.5 L/ha (0.5 ml/1 L water) Day 05 Potassium bicarbonate 0.02 kg/1 L water Day 0 and 7***6 K50 (potassium bicarbonate)

+ wetter (SW7)3 L/ha (3 ml/1 L water)+100 ml/ha (0.1 ml/1 L water)

Day 0 and 7

7 Sodium silicate 1% v/v (10 ml/1L water) Day 0 and 78 Milsana® (giant knotweed extract) 0.15 % v/v (1.5 ml/ 1 L water) Day 0 and 79 di-potassium hydrogen phosphate 1% w/v (10 g/ 1 L water) Day 0 and 710 Paraffinic oil 1.5 % v/v (15 ml/ 1 L water) Day 0 and 7*In 100 ml water/m2 (equivalent to 1000 L/ha)**Plants inoculated with powdery mildew on day 4**Reduced to 0.01 kg/L water at day 7 because of scorch

For each crop, a plot comprised five pots placed on capillary matting in a plastic tray. Trays were spaced at least 30 cm apart. For apple mint, pots each contained one rooted cutting. For parsley, pots each contained a standard

SID 5 (Rev. 3/06) of 26

number of seedlings as provided by the commercial nursery. Each treatment was replicated four times in a randomised block design and statistical analysis was by analysis of variance (ANOVA) in Genstat.

Spray treatments were applied using an Oxford precision sprayer, with single 02F110 nozzle and guard (to prevent spray drift). Treatments applied are described in Table 5 and product details are given in Table 6.

Table 6. Approval status of the products applied and the basis for selecting the rates used

Product Approval NotesAmistar (250g/L azoxystrobin)

SOLA 0659/03 Syngenta

Thiovit Jet (80 % w/w sulphur)

SOLA 3652/02 Syngenta

Experimental product (NF 149)

AEA Use likely maximum label rate

Potassium bicarbonate(99 %)

COMM 1/4/04 Food grade commodity substance application

Maximum approved rate

K50 (50 % potassium bicarbonate) + wetter (SW7)

- Omex Nutrient application Rates suggested by Omex (pers.

comm. G. Bahari)

Sodium silicate - Fisher Scientific Rate from literature (Belanger et

al., 1995)

Milsana® (giant knotweed extract) - Dr Schaette elicitor of Reynoutria sachalinensis

Manufacturer recommended rate (pers. comm. S. Reissner, Biofa GmBH)

di-potassium hydrogen phosphate - Fisher Scientific Rate from literature (Casulli, F. et

al., 2000)

Paraffinic oil - Loveland Highly refined, food grade

paraffinic oil Rate from studies on grapes in

US (A. Schilder, pers.comm)

Four days after spray 1, infector plants of apple mint and parsley with typical symptoms of powdery mildew were introduced into the appropriate glasshouse (one plant in the centre of each plot). Apple mint plants were naturally infected with Erysiphe biocellata and parsley plants were naturally infected with E. heracleum. Using spare infected material, spore suspensions of powdery mildew from apple mint and parsley were prepared in sterile distilled water (1 x 105 spores/ml) and applied to the appropriate crop using a hand-held mister, to the point of run-off. Each crop was covered with a polythene ‘tent’ overnight (18 h) to provide conditions of high relative humidity. The infector plants were removed from the glasshouse compartments 7 days after the 2 nd spray. To provide conditions conducive for powdery mildew development, the glasshouse compartments were shaded from the time of inoculation. Plants were hand-watered as required but were kept under fairly dry conditions to facilitate powdery mildew development.

There were three assessments of disease incidence and severity commencing 11 days after inoculation (7 days after the 2nd fungicide application). For each pot, the severity of powdery mildew was assessed by estimating the percentage leaf area affected. In addition, the incidence of any phytotoxic or beneficial effects of spray treatments was recorded.

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Experiment 2The experiment was sited in a glasshouse compartment at ADAS Arthur Rickwood, Cambridgeshire in September 2005. Apple mint was supplied as plugs of rooted cuttings from a commercial pot herb nursery and was used 4 weeks after rooting. Because of the high risk of powdery mildew at the nursery, plug plants were treated with 2% potassium bicarbonate + 0.1% Activator 90 (non-ionic wetting agent) by the grower 1 week prior to trial commencement. The individual plugs were transferred to F1 compost in 9 cm diameter pots (one plant per pot) and placed in trays in a glasshouse (12-15oC, ambient light).

A plot comprised five pots each containing one rooted cutting, placed on capillary matting in a plastic tray. Trays were spaced at least 30 cm apart. Each treatment was replicated four times in a randomised block design and statistical analysis was by analysis of variance (ANOVA) in Genstat. Spray treatments were applied using an Oxford precision sprayer, with single 02F110 nozzle and guard (to prevent spray drift). Treatments applied are described in Table 7. The rate of potassium bicarbonate was reduced compared to experiment 1 and a wetter (Silwet L-77) was used. Silwet L-77 was also used together with Thiovit Jet. Milsana was used with a wetter recommended by the manufacturer.

Table 7. Programmes tested for control of powdery mildew on apple mint.

Treatment Application rate* Timing 1 Untreated control - -

2 Potassium bicarbonate + Silwet L-77Potassium bicarbonate + Silwet L-77

0.25% w/v (2.5 g/L) +0.1 ml/L 0.25% w/v (2.5 g/L) +0.1 ml/L

3 d before inoc7, 14 and 21 d after inoc

3 Amistar Potassium bicarbonate + Silwet L-77

1 L/ha (1 ml/L)0.25% w/v (2.5 g/L) +0.1 ml/L


4 Thiovit Jet + Silwet L-77Potassium bicarbonate + Silwet L-77

0.005 kg/5 L (1 g/L) +0.1 ml/L0.25% w/v (2.5 g/L) +0.1 ml/L


5 K50 + SW7K50 + SW7

3 L/ha (3 ml/L) + 0.1 ml/L3 L/ha (3 ml/L) + 0.1 ml/L


6 Amistar K50 + SW7

1 L/ha (1 ml/L water)3 L/ha (3 ml/L) + 0.1 ml/L


7 Thiovit Jet + Silwet L-77K50 + SW7

0.005kg/5 L (1 g/L) + 0.1 ml/L3 L/ha (3 ml/L) + 0.1 ml/L


8 Milsana® + T/S ForteMilsana® + T/S Forte

0.15 % v/v (1.5 ml/L) + 2.5 ml/L0.15 % v/v (1.5 ml/L) + 2.5 ml/L


9 Experimental 1** Experimental 1

1 ml/L 1 ml/L


10 Experimental 2**Experimental 2

1.6 ml/L1.6 ml/L


*in 100 ml water/m2 (equivalent to 1000 L/ha)**Experimental products containing low concentrations of copper ions

Three days after spray 1, the experiment was inoculated as described for experiment 1. Plants were also maintained as described in experiment 1.

There were four assessments of disease incidence and severity commencing 11 days after inoculation. For each pot, the severity of powdery mildew was assessed by estimating the percentage leaf area affected. In addition, the incidence of any phytotoxic or beneficial effects of spray treatments was recorded.

3.3.3. Results

Experiment 1

SID 5 (Rev. 3/06) of 26

On parsley, symptoms of powdery mildew were first observed on untreated plots 9 days after artificial inoculation. At 11 days after inoculation, all of the treatments had significantly reduced disease severity to 13% or less compared to 47% in the untreated control (P<0.001). Disease severity had exceeded 90% by 18 days after inoculation on the untreated control (Figure 2a) demonstrating high inoculum pressure. At 24 days after inoculation (21 days after the 2nd spray application) the best level of control was maintained in plots where Thiovit Jet or K50 + wetter had been applied, with a significant reduction in disease severity from 91% in the untreated control to approximately 35% (P<0.001).

a) Parsley

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Days after inoculation

% le

af a

rea

affe

cted

ControlAmistarThiovit JetExperimentalPotassium bicarbonateK50 + w etterSodium silicateMilsanaDi-potassium hydrogen phosphateParaffinic oil

b) Apple mint

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 30

Days after inoculation

% le

af a

rea

affe

cted

ControlAmistarThiovit JetExperimentalPotassium bicarbonateK50 + wetterSodium silicateMilsanaDi-potassium hydrogen phosphateParaffinic oil

Figure 2. Effect of treatments on powdery mildew severity on three assessment dates.

On apple mint, symptoms of powdery mildew were first observed on untreated plots 9 days after artificial inoculation. At 11 days after inoculation, all of the treatments had significantly reduced disease severity to 4% or less compared to 19% in the untreated control (P<0.001). Disease severity was approximately 40% by 18 days after inoculation on the untreated control (Figure 2b) demonstrating high inoculum pressure. At 24 days after

SID 5 (Rev. 3/06) of 26

inoculation (21 days after the 2nd spray application) the best level of control was maintained in plots where Amistar, Thiovit Jet or Milsana® had been applied, with a significant reduction in disease severity from 40% in the untreated control to 8% or less (P<0.001). Treatment with 2% potassium bicarbonate led to symptoms of phytotoxicity on both parsley (bleached leaves) and apple mint (leaf necrosis). Subsequent testing with 1% and 0.5% potassium bicarbonate on untreated apple mint plants also resulted in leaf necrosis. Treatment with sodium silicate resulted in leaf edge necrosis on mint. There were no beneficial growth effects of treatments applied.

Experiment 2Powdery mildew was first observed 11 days after inoculation. All or the programmes except the experimental products (treatments 9 and 10) gave excellent powdery mildew control with percentage leaf area affected remaining at less than 3% at 25 days after inoculation (3 October 2005), compared with 25% in the untreated control (Figure 3). Two weeks after the final spray application, disease severity was 7% or less for all the spray programmes (except the experimental products) compared to 48% in the untreated control. Use of Amistar or Thiovit Jet at the beginning of a programme (treatments 3, 4, 6 or 7) did not give a significant reduction in disease compared to programmes without these fungicides (treatments 2, 5 and 8). No symptoms of phytotoxicity or beneficial growth effects were observed in this experiment.

0

10

20

30

40

50

60

15/09/2005 20/09/2005 25/09/2005 30/09/2005 05/10/2005 10/10/2005 15/10/2005

Date

% le

af a

rea

affe

cted

Control

Bicarb, Bicarb

Amistar, Bicarb

Thiovit Jet, Bicarb

K50, K50

Amistar, K50

Thiovit Jet, K50

Milsana, Milsana

Product A, Product A

Product B, Product B

Spray 2

Spray 3

Figure 3. Effect of treatment programmes on the severity of powdery mildew on apple mint.

3.3.4. Discussion

Both experiments were done under high inoculum pressure, providing a rigorous test of the products used. Thiovit Jet was an effective protectant on both crops in experiment 1 and on mint in experiment 2. A single application of Amistar (following SOLA conditions of use) did not provide effective control of powdery mildew on parsley but gave good disease control on apple mint in experiment 1, and was effective as a protectant when followed by applications of K50 or potassium bicarbonate in experiment 2. Despite reduction in the application rate, the efficacy of potassium bicarbonate (food-grade) improved in experiment 2 when it was used together with a wetter. Regular sprays with either potassium bicarbonate or K50 used with an appropriate wetter provided effective powdery mildew control on apple mint irrespective of whether a conventional fungicide had been applied as the first spray.

Milsana® showed promise against powdery mildew on apple mint in experiment 1 but was less effective against powdery mildew on parsley. Following advice from the supplier, Milsana® was used together with a wetter in

SID 5 (Rev. 3/06) of 26

experiment 2 and checked powdery mildew development on apple mint when it was applied at weekly intervals. Milsana® (extract of giant knotweed) is produced and registered in Germany as a ‘plant strengthener’, with published reports of efficacy against powdery mildew, by triggering plant defence responses.

Phytotoxicity following use of potassium bicarbonate on herbs (experiment 1) has also been observed by some herb growers but does not occur consistently. When potassium bicarbonate was used at a lower rate (0.25%) and together with a wetter in experiment 2, symptoms of phytotoxicity were avoided. The symptoms resulting from use of sodium silicate were most likely due to the high pH of the compound.

In experiment 2, the increase in disease severity following the final spray treatment demonstrated that with products such as potassium bicarbonate (either as food-grade or K50) or Milsana®, regular sprays (7-10 day interval) are needed to keep the disease under check, particularly under conditions of high inoculum pressure.

It is known that sulphur can have a deleterious effect on certain organisms used for biological pest control with protected herb systems. Further work is required to identify the compatibility of other products highlighted in this experiment, with biological control agents used in IPM programmes.

3.4. Effect of compost amendments on coriander root rot caused by Pythium sp.

3.4.1. Introduction

Treatments applied as compost amendments were evaluated for their effects against damping-off caused by Pythium sp. on coriander. All of the products are available in the UK for use either as soil amendments, plant nutrients, plant ‘strengtheners’ or ‘growth enhancers’.

3.4.2. Methods

Compost amendment treatments tested against coriander root rot are listed in Table 8. A plot comprised three pots each sown with 20 coriander seeds. There were four replicate plots for each treatment laid out in a randomised block design. Data on percentage emergence was analysed by ANOVA. Scores for root health were analysed using Friedman’s test for non-parametric data.

Table 8. Compost amendment treatments tested against coriander root rot (Pythium sp.)

Compost inoculated with Pythium sp.

Compost amendment Recommended incorporation rate

Product amount in 4 L compost

1 No Nil - -*2 Yes Nil - -*3 Yes Gliomix (Gliocladium

catenulatum)5 g per 100 L growth substrate

2.0 g in 1 L water

4 Yes Stimagro (Streptomyces griseoviridis)

Varies 0.1 g in 1 L water

5 Yes Agralan Revive 1 ml per 10 L compost 0.4 ml in 1 L water6 Yes Polyversum® (Pythium

sp.) 100 g/ha in 1000 L water 0.1 g in 1 L water

7 Yes Chitin (crab shells) 10 g/L compost 40.0 g*8 Yes Trianum-G (Trichoderma

harzianum)750 g/m3 3.0 g*

9 Yes Experimental product** 1.6 ml/L 1.6 ml in 1 L water10 Yes Orophite 5 ml/L 5 ml in 1 L water

*Product incorporated then 1 L distilled water added to compost.**Experimental product containing a low concentration of copper ions

Twenty plates of Pythium sp. ex coriander (on potato dextrose agar amended with streptomycin) were homogenised in a Waring blender and then mixed thoroughly with 36 L of M3 compost. The infested compost was divided into nine batches (4 L) in separate containers and kept moist. One 4L batch of non-infested compost was also required.

The compost amendments were applied 9 days after compost infestation with Pythium sp. (see Table 8). Each treatment was watered to ensure the compost was wet. The treatments were kept in separate containers and stored in a glasshouse. Four days after compost amendments were done, 9 cm pots were filled with the compost treatments. Twenty coriander seeds were laid on the compost surface of each pot and covered with a thin layer of compost mixed with autoclaved sand (75% sand v/v). The trial was laid out in a randomised block design in a

SID 5 (Rev. 3/06) of 26

glasshouse. The pots in saucers were maintained at a minimum of 20oC (ambient light) with daily watering from above to keep the compost moist, until at least 50% emergence had occurred. After this stage, watering was from the base.

Seed germination was assessed 16 days after sowing. Approximately 4 weeks after sowing, germination was assessed again and plants scored for root vigour. Roots were floated in sterile distilled water to check for oospores of Pythium.

3.4.3. Results and discussion

Percentage germination was significantly reduced for all of the inoculated treatments compared with the uninoculated control (Table 9). Oospores of Pythium sp. were observed microscopically in the roots of coriander seedlings grown in inoculated compost, confirming damping-off due to Pythium sp. as the cause of poor germination. None of the amendment treatments significantly reduced coriander root rot compared with the inoculated control. There was no significant effect of treatment on root vigour, although there was a trend for healthier roots in the uninoculated control treatment. Lack of disease control can be partly attributed to high inoculum pressure and further work may be warranted to test the treatments under more natural infection conditions.

Table 9. Effect of inoculation with Pythium sp. and compost amendments on the germination and root health of coriander seedlings

Compost inoculated with Pythium sp.

Compost amendment

Mean no. seeds germinated

Root vigour score*

No Nil 15.1 4.6Yes Nil 8.8 2.6Yes Gliomix 9.6 2.8Yes Stimagro 8.8 3.6Yes Agralan Revive 9.1 2.7Yes Polyversum® 9.7 3.4Yes Chitin (crab shells) 6.8 2.0Yes Trianum-G 9.1 3.1Yes Experimental

product8.3 3.3

Yes Orophite 9.8 3.5d.f.

S.e.d.27

1.68d.f.

P9

0.098

*1=completely rotted; 5=healthy (analysed by Friedman’s Test)

4. OBJECTIVE 3: to formulate Best Practice Guidelines for integrated pest and disease control on protected herbs and deliver to the protected herb industry.

Status: Ongoing

During the project, information on integrated pest and disease control on protected herbs has been formulated and delivered to the industry in a range of formats including Best Practice Guidelines (to be published by HDC), the project website, three workshops for growers, five publications in the trade press, 14 presentations at conferences and growers events, and advice to individual growers. At the start of the project, a steering committee was formed comprising members from five sectors of the protected herb industry, plus representatives from HDC and Defra. In addition to formal meetings with the steering committee (December 2003 and November 2004), there has been ongoing communication between members of the project and the steering committee, to ensure that knowledge transfer from the project remains relevant to the needs of the protected herb industry.

4.1. Best Practice Guidelines

The Best Practice Guidelines for integrated pest and disease management for protected herbs are being produced in conjunction with HDC. Following discussion with the project steering committee as to the most appropriate format, the best-practice guideline handbook will be produced in an A5 ring-binder format to provide a

SID 5 (Rev. 3/06) of 26

useful reference tool for nursery staff. The contents have been agreed with the HDC communications manager and a key grower, and are listed below. Best-practice guidelines will be forwarded to HDC for editing and page-setting. The guidelines will also be added to the project website at www.protectedherbs.org.uk. It is anticipated that all text, images and figures will be delivered to HDC by the end of March 2007, for subsequent handbook production.

4.1.1. Handbook Contents

Title page Contents Introduction Disclaimer Protected herb production and importance of IPM

- Diversity of the industry (crops, production and propagation systems)- Limitations to pesticide use (limited availability, retail demands, harvest intervals, MRLs)

Principles of IPM- Introduction- Prediction, monitoring and diagnosis - Cultural controls

- Host plant resistance- Seed and planting material health- Nursery hygiene- Soil and environmental conditions- Water treatment- Soil treatment (disinfection, flaming etc)

- Natural products for disease control- Biological pest control- Use of pesticides and fungicides as a component of IPM

Sections 1 and 2: Integrated pest and disease management respectively

Best Practice Guidelines for the most effective integrated management strategies for each of the priority pests and diseases (listed in Tables 1 and 2) will be given. Guidelines will include photographs for recognition of pests, pest damage and diseases, and cultural, biological and chemical control options within integrated programmes on herbs grown under different production situations. Any new options arising from the experimental work completed in Objective 2 will be included. An example Best-practice guideline is given in Appendix I.

Appendices- Fungicides and pesticides currently approved for use on protected herbs and efficacy for different pests

and diseases (2 tables). - Pesticide compatibility with biological control agents (1 table, split into fungicides and pesticides).- Suppliers of biological control agents and natural products.- Table of high risk periods for key pests and diseases on key protected herb crops.- Legislation regarding use of pesticides and biological control agents.- Plant health policy to prevent spread of non-indigenous pests and diseases.- Useful sources of information.

4.2. Project website

The project website (www.protectedherbs.org.uk) was launched in September 2004. It includes the following features:

Photographs and notes to aid identification of pests, pest damage and diseases of protected herbs. Results of validation experiments done in Objective 2 during the project. Best Practice Guidelines for integrated management of pests and diseases on protected herbs.

Use of the website has been demonstrated at several grower events (BHTA technical meetings, BHTA annual conference, and grower workshops). One technical manager from a herb nursery noted how useful the website has been for training nursery staff in pest and disease identification.

Discussions are ongoing to arrange for the website to be hosted in the longer term by the HDC, thus ensuring that all of the information remains in the public domain.

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4.3. Workshops

A workshop was held at each of three locations (Cambridgeshire, Worcestershire and West Sussex) in September 2006, to provide training for growers and other members of the protected herb industry, in accurate pest and disease recognition, and the use of integrated management strategies. Research results were presented from this project and also from other recent or current Defra and HDC-funded projects. The workshops were organised and presented by ADAS staff, led by Jude Bennison and Kim Green, with assistance from Heather Maher and Kerry Maulden. HDC provided administrative and financial support. Practical sessions provided delegates with the opportunity to examine pest and disease samples and biological control agents, and to use the project website. A total of 47 delegates attended the three workshops, including growers, consultants, seed suppliers and members of the agro-chemical industry. Training materials were provided in the form of booklets containing colour reproductions of the PowerPoint presentations. BASIS and NRoSO points were awarded.

At each workshop, delegates were asked to provide feedback on the usefulness of the training event. Example comments were as follows:

‘Very useful presentations, handouts and practical session’. ‘The information was presented in a user-friendly way’. ‘I can’t think of any possible improvements to the workshop- very good!’ ‘I will use more biological control methods on my own nursery as a result of this workshop’. I will try some of the new methods for biological control that were demonstrated’. ‘I will pursue disease control methods where I’ve not been too successful in the past’ ‘More similar workshops next year please’.

An overview of the workshops was published in the November 2006 edition of ‘HDC News’.

Figure 4. Participants during a practical session at the protected herb workshop in Chichester

4.4. Publications

See Section 9 (References to published material)

4.5. Presentations

J. Bennison presented the aims of the project in a presentation entitled ‘Integrated pest management on protected herbs’ at the Annual Conference of the British Herb Trade Association, Norwich, 24 January 2004.

J. Bennison presented project results at a technical exchange meeting with Certis in November 2004.

T. O’Neill presented results from a powdery mildew experiment at a training workshop at WJ Findons Nursery, Stratford upon Avon in November 2004.

K. Green presented project results at a Technical Meeting of the British Herb Trade Association, National Herb Centre, 23 March 2005.

J. Bennison presented a paper on the project at the IOBC meeting of the Working Group ‘Integrated control in protected crops, temperate climate’ in Finland (May 2005).

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K. Green presented project results as part of a presentation on ‘Plant biopesticides and biostimulants – recent research results’ at an HDC/BOPP Seminar ‘Technical Developments in the Ornamentals Sector’, Nottingham, 22 June 2005.

J. Bennison presented ‘Biological control of pests on protected herbs’ at the AAB meeting ‘Insecticide-free pest management’, Peterborough, 29 September 2005.

K. Green presented a seminar on ‘Integrated disease management on protected herbs’ at the Annual Conference of the British Herb Trade Association, Exeter, 21 January 2006 (Milestone 03/04).

K. Green and J. Bennison presented project results at a Technical Meeting of the British Herb Trade Association, National Herb Centre, 21 March 2006.

J. Bennison presented results of the project in ‘Advances in biological pest control’ at the BOPP AGM at Sutton Bonington, 28 June 2006.

D. Hand presented project results in ‘Biological control of pests on protected herbs’ at the AAB meeting ‘Insecticide-free food; British salads leading the way’, Peterborough, 12 July 2006.

J. Bennison and K. Green presented ideas for future research based on findings from the current project at an ADAS/HDC/herb industry meeting, ADAS Boxworth, 6 October 2006.

J. Bennison presented ideas for future research based on findings from the current project at a Technical Meeting of the British Herb Trade Association, National Herb Centre, 25 October 2006.

J. Bennison presented the aims and results of the project at the Australian Herbs and Spices Industry Association (AHSIA) workshop ‘Herbs….more than just a bit on the side’, Adelaide, on 4-5 September, 2006. The visit to Australia was funded by the AHSIA.

4.6. Other technology transfer

Project results on powdery mildew control using potassium bicarbonate products were included in a report to HDC, co-authored by K. Green in June 2005 (HDC project CP 48).

Technical knowledge gained from the project was used in writing/editing HDC-commissioned pest and disease cards on herbs for growers. The first five identification cards were produced in August 2005. A further nine pest and disease cards were published and mailed to the industry in January 2007.

Seven herb nurseries were visited to discuss pest and disease problems and management strategies with growers.

Telephone/technical advice on aspects of the project was provided to six herb growers.

More than 30 pest and disease samples were identified for growers.

Experiment results were discussed with suppliers of biological and other novel products used in the trials.

J. Bennison and K. Green met with Mike Caddy (AgrexCo) and herb experts from the Ministry of Agriculture in Israel, to discuss pest and disease management strategies and potential avenues for increased knowledge transfer (23 June 2005).

5. CONCLUSIONS

5.1 Objective 1. To collate and evaluate currently available information on potential integrated management solutions for priority pest and disease problems on protected herbs.

Collation and evaluation of currently available information for pest and disease management on protected herbs highlighted the following issues:

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For many key pests and pathogens (e.g. thrips, and grey mould caused by Botrytis cinerea), there is a wealth of existing information on integrated management strategies for other protected crops, that can be put immediately into use by protected herb growers, to reduce or replace the need for chemical control.

However, due to the diverse nature of the protected herb industry (with many crops, pest and disease problems, and production systems), generic solutions for pest and disease control are not always appropriate. For example, the whitefly parasitoid, Encarsia formosa, which is highly effective on many protected salad and ornamental crops, gives unreliable control on herbs. This could be due to many possible factors, including host plant characteristics such as the strong scent and hairy leaves of many susceptible herbs acting as deterrents for E. formosa. In addition, for herbs grown in polythene tunnels and unheated glasshouses, temperatures can be to cool for E. formosa activity for key periods in the production cycle. Thus, further research is needed to develop specific integrated management strategies for certain pests and diseases on herbs.

5.2 Objective 2. To evaluate control strategies for selected pest and disease problems using representative host plant species and production systems.

Three biological control agents were evaluated for the control of shore flies on potted mint. None of the individual treatments (the entomopathogenic nematodes, Steinernema feltiae; the predatory mites, Hypoaspis aculeifer and the predatory beetles, Atheta coriaria), reduced numbers of shore flies at commercially acceptable application rates. The combination of the three biological control agents reduced numbers of shore flies at the marketing stage from 2.3 per pot in untreated controls to 0.4 per pot, but it is possible that the naturally occurring shore fly parasitoid, Aphaereta debilitata, also contributed to control. An opportunity was identified for improving the establishment and cost-effectiveness of A. coriaria and this led to a subsequent HDC-funded project (see Section 6, Future Work).

Two biological control agents were identified as having potential for the control of the ‘sage’ leafhopper, Eupteryx melissae. The leafhopper egg parasitoid, Anagrus atomus reduced mean numbers of leafhoppers on mint and sage, from 54 per plant in the untreated controls, to 12 per plant. The entomopathogenic nematodes, Steinernema feltiae increased the proportion of dead leafhoppers per sage leaf from 5% on water-treated leaves to 65% on nematode-treated leaves. Further development work is required to determine effective rates, timings and application strategies for both biological control agents, for effective control of leafhoppers on protected herbs.

Alternatives to conventional fungicides were identified for powdery mildew control on protected herbs. Even under high disease pressure, weekly sprays of 0.25% potassium bicarbonate (food-grade) + wetter, K50 (50% potassium bicarbonate; 3 L product/ha) + wetter, or 0.15% Milsana® (giant knotweed extract) + wetter, reduced percentage leaf area affected on apple mint, from 25% in the untreated control to less than 3%. Rapid disease development once the spray programme was complete demonstrated that regular sprays with such products are required to maintain effective powdery mildew control.

The following treatments as compost amendments were evaluated for their effects on coriander root rot (Pythium sp.) in an inoculated pot experiment: Gliomix, Stimagro, Agralan Revive, Polyversum®, Trianum-G, chitin and an experimental product. None of the amendment treatments significantly reduced coriander root rot compared with the inoculated control, due partly to high inoculum pressure. Further work may be warranted to test the treatments under more natural infection conditions.

5.3 Objective 3. To formulate Best Practice Guidelines for integrated pest and disease control on protected herbs and deliver to the protected herb industry.

Best practice guidelines for integrated pest and disease control on protected herbs have been effectively and extensively communicated to the industry using a range of knowledge transfer methods (practical workshops, website, conference presentations and trade-press articles). Positive feedback from industry attendees confirmed that practical workshops had provided a particularly useful forum for communicating key messages. The format and contents of a handbook has been agreed with industry and is being produced in conjunction with HDC.

6. FUTURE WORK

Building on the results of year 1 research on biological control of shore flies, an HDC-funded project led by Jude Bennison started on 1 September 2005. The project (PC 239) is entitled ‘Protected herbs, ornamentals and celery: development of an on-nursery rearing system for Atheta coriaria for reduced cost biological control of sciarid and shore flies. Stockbridge Technology Centre is collaborating in the project and Syngenta Bioline is an in-kind industry partner. The year 1 report is available from the HDC.

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Jude Bennison provided information and industry contacts from this project and from HDC-funded project PC239 to a PhD student at York University, who is researching the biology and potential of naturally-occurring shore fly parasitoids. The HDC project and the PhD project may lead to further industry-funded research.

Year 2 results with testing the egg parasitoid, Anagrus atomus and the entomopathogenic nematode, Steinernema feltiae (‘Nemasys F’) for biological control of the ‘sage’ leafhopper, Euptertyx melissae were promising and warrant further investigation, due to the lack of a commercially available biological control strategy for this pest.

Australian herb growers have expressed an interest in developing a similar project to this one, but relevant to their own problems and production systems. There is scope for developing a new collaborative project between ADAS, Australian scientists and the Australian Herbs and Spices Industry Association (AHSIA). Following Jude Bennison’s visit to Australia in September 2006, she and Kim Green contributed to a joint proposal to the Australian Rural Industries Research and Development Corporation to develop the project with relevant scientists and industry members. The outcome of the proposal is due in February 2007.

Experiment results demonstrated that powdery mildew on protected mint can be effectively managed without synthetic fungicides, using potassium bicarbonate products or Milsana® (marketed in Germany as a ‘plant enhancer’) using appropriate rates, timings and wetters. It will be essential to identify the compatibility of any such products with biological control agents used in IPM programmes. Future work on this aspect was included in a full proposal to the Pesticides Safety Directorate (PSD) in response to open competition CTX0514 but did not receive funding.

There is scope for further detailed experimentation using the range of compost amendment products now available, to enable improved management of damping-off and root rots in protected herbs.

In response to requests from members of the British Herb Trade Association, the following concept notes on outdoor herbs were submitted for consideration by the HDC Field Vegetable panel in October 2006: ‘Outdoor herbs: integrated management of foliar diseases’ submitted by Kim Green. The panel requested a

full proposal for the March 2007 meeting and this was submitted in January 2007. ‘Field-grown herbs: evaluation of a mechanical method for the cultural control of leafhoppers’ was submitted

by Jude Bennison. The panel requested a full proposal for the March 2007 meeting and this was submitted in January 2007.

7. ACKNOWLEDGEMENTS AND LITERATURE CITED

ACKNOWLEDGEMENTS

Thanks to the following:

Project Steering Group Tom Davies, Malvern View Herbs Laurie Reed, Yorkstock Herbs Chris Nye, CN Seeds Ltd. John Overvoorde, Delfland Nursery Humber VHB representatives

Provision of trial sites, plants and materials for project All steering group members Humber VHB Swedeponic UK Ltd National Herb Centre Biological control suppliers Other industry members

LITERATURE CITED

Belanger, R.R., Bowen, P.A., Ehret, D.L. & Menzies, J.G.. 1995. Soluble silicon: its role in crop and disease management of greenhouse crops. Plant Disease 79: 329-335.

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Carney, V.A., Diamond, J.C., Murphy, G.D. & Marshall, D. 2002. The potential of Atheta coriaria Kraatz (Coleoptera: Staphylinidae), as a biological control agent for use in greenhouse crops. IOBC/wprs Bulletin 25(1): 37-40.

Bennison, J. 2001. Protected herbs: control of glasshouse whitefly and leafhoppers within IPM programmes. HDC Final report for project PC 178.

Bennison, J. 2006. Exploting knowledge of western flower thrips behaviour to improve efficacy of biological control measures. Defra final report for project HH3102TPC.

Bennison, J. 2007. Protected herbs, ornamentals and celery: development of an on-nursery rearing system for Atheta coriaria for reduced cost biological control of sciarid and shore flies. HDC Annual report for project PC 239.

Casulli, F., Santomauro, A. & Faretra, F. 2000. Natural compounds in the control of powdery mildew on Cucurbitaceae. EPPO Bulletin 30: 209-212.

Herard, F. & Chen, K. 1985. Ecology of Anthocoris nemorum (L.) (Het.:Anthocoridae) and evaluation of its potential effectiveness for biological control of pear psylla. Agronomie 5(10): 885-863.

Malais, M.H. & Ravensberg, W.J. (1992). Knowing and recognising. The biology of glasshouse pests and their natural enemies. Koppert B.V. and Reed Business Information, The Netherlands, 244-255.

Miller, K.V. & Williams, R.N. 1983. Biology and host preference of Atheta coriaria (Coleoptera: Staphylinidae), an egg predator of Nitidulidae and Muscidae. Annals of the Entomological Society of America 76: 158-161.

Vanninen, I. & Koskula, H. 2003. Biological control of the shore fly (Scatella tenuicosta) with Steinernematid nematodes and Bacillus thuringiensis var. thuringiensis in peat and rockwool. Biocontrol Science and Technology 13: 47-63.

Vanninen, I. and Koskula, H. 2004. Biocontrol of the shore fly Scatella tenuicosta with Hypoaspis miles and H. aculeifer in peat pots. BioControl 49 (2): 137-152.

References to published material9. This section should be used to record links (hypertext links where possible) or references to other

published material generated by, or relating to this project.

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Project website at www.protectedherbs.org.uk

Bennison J & Green K. 2004. Integrated control of pests and diseases on protected herbs. ADAS bedding and pot plant notes for growers, December 2004.

Bennison J & Green K. 2005. Integrated pest and disease control in protected herbs. In: Plant it! Defra R&D Newsletter for Horticulture & Potatoes, Plant Genetic Resources and Plant Varieties and Seeds, Issue 7 (January 2005).

Bennison J & Green K. 2005. Better control of pests and diseases. HDC News. April 2005, 19-21.

Bennison J, Green K & O’Neill T. 2005. Best practice guidelines for integrated pest and disease management on UK protected herbs. IOBC/wprs Bulletin Vol. 28(1) 2005:15-18.

Green K. 2006. Protected herbs: best practice guidelines for integrated pest and disease management. 1. Septoria leaf spot (Septoria spp.). BHTA News (Newsletter of the British Herb Trade Association), December 2006.

HDC. 2005. Pest and Disease Cards for Herb Growers. East Malling: Horticultural Development Council.

Tiffin, D. & Green K. 2005. Use of potassium hydrogen carbonate (potassium bicarbonate) for powdery mildew control. Final report for HDC project CP 48. East Malling: Horticultural Development Council. 30 pp.

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