Nematode Thresholdsand

Damage Levelsfor

California Crops

Howard Ferris

Some of those involved….

• Dan Ball• Larry Duncan• Pete Goodell• Joe Noling• Diane Alston• Sally Schneider• Lance Beem

That initial population at which the difference in crop value with and without management is equal to the cost of the management

The Economic Threshold amended

• Most nematode management decisions made before planting• Pest population already present• Pest population measurable• Growing conditions are stable

– temperature, moisture– time of planting

Nematode population dynamics should be stableDamage should be predictable

Premises:

Thresholds by field plot

South Coast Field StationUSDA ShafterTulelake

Thresholds by transectImperial and Coachella Valleys

Ventura CountyTulare County

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Economic Threshold – Discrete Costs Model

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Optimization – Continuous Costs Model

Seinhorst Damage Function

• Y=m+(1-m)z(Pi-T)

• Y=relative yield• m=minimum yield• Z=regression parameter• Pi=population level• T=tolerance level

• Based on preplant population levels – measured or predicted from overwinter survival rates

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Case Study on Cotton

Cultivar Soil Location (T)olerance Z m

SJ2 loamy sand south SJV 65 0.998 0.55

Deltapine loamy sand imperial 50 0.9972 0.65

SJ2, SJ5, SJ-C1 l. sand/s. loam south SJV 55 0.999 0.48

average (all) --------------------- ------------- 57 0.998 0.56

average (SJV) --------------------- ------------- 60 0.9985 0.52

SJ2(-FOV) sandy loam south SJV 55 0.9966 0.54

SJ2(+FOV) sandy loam south SJV 55 0.9847 0.38

Meloidogyne incognita, J2/250 cc soil

Expected % yield loss at different preplant nematode densities

Cultivar Soil Location Threshold 20 50 100 200 500

SJ2 loamy sand south SJV 25 0 5 15 27 41

Deltapine loamy sand imperial 19 0 7 16 26 34

SJ2, SJ5, SJ-C1 l. sand/s. loam south SJV 21 0 4 10 19 37

average (all) --------------------- ------------- 22 0 6 15 27 40

average (SJV) --------------------- ------------- 23 0 5 12 24 41

SJ2(-FOV) sandy loam south SJV 21 0 10 23 37 45

SJ2(+FOV) sandy loam south SJV 21 0 42 59 62 62

Case Study on Cotton

Damage Function Parameters for Selected Crops

Crop (T)olerance Z mBell Pepper 65 0.9978 0.87Cantaloupe 10 0.9972 0.40

Carrot 0 0.99 0.6Chile Pepper 39 0.9934 0.70Cotton 57.5 0.9976 0.6Cowpea 22 0.9816 0.96

Potato 18 0.99 0.49Snapbean 14 0.9978 0.57Squash 0 0.9898 0

Sugarbeet 0 0.9955 0.89Sweetpotato 0 0.99375 0.47Tomato 41.8 0.99934 0.47

Thresholds and Expected Yield LossMeloidogyne incognita, J2/250 cc soil; adjusted for extraction efficiency

Expected % yield loss at different preplant nematode densitiesCrop Threshold 1 2 5 10 20 50 100 200Bell Pepper 25 0 0 0 0 0 2 5 8

Cantaloupe 4 0 0 1 3 7 17 30 46

Carrot 0 1 2 5 9 16 29 37 40

Chile Pepper 15 0 0 0 0 3 14 24 30

Cotton 22 0 0 0 0 0 6 15 27

Cowpea 52 0 0 0 0 0 0 6 8

Potato 7 0 0 0 4 15 34 47 51

Snapbean 5 0 0 0 1 3 10 18 29

Squash 0 3 5 12 23 41 74 93 100

Sugarbeet 0 0 0 1 1 2 5 8 10

Sweetpotato 0 1 2 4 8 15 30 43 51

Tomato 16 0 0 0 0 0 3 7 14

Expected DamageMeloidogyne chitwoodi; summer crop potato; Klamath BasinFall population levels; adjusted for extraction efficiency

Expected % tuber blemish at different fall nematode densities

J2/250 cc 1 2 5 10 20 50 100 200 500

% Blemish 3 4 5 7 8 12 15 18 25

temporalavoidance

Thresholds and Expected Yield Loss

Cultivar Soil Location (T)olerance Z m

US-H9 clay Imperial 100 0.99886 0

US-H9 loam SJV/Idaho 300 0.99976 0

Heterodera schachtii, eggs/100g soilSugarbeets

Cultivar Soil Location Threshold 50 100 200 500 1000US-H9 clay Imperial 100 0 0 11 37 64

US-H9 loam SJV/Idaho 300 0 0 0 5 15

Expected % yield loss at different preplant nematode densities

Data from P.A. Roberts

Optimized Discrete Model

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Some ReferencesBenedict, J.H., K.M. El-Zik, L.R. Oliver, P.A. Roberts, and L.T. Wilson. 1989. Economic injury levels for cotton pests. Chapter 6.

In: Integrated Pest Management Systems and Cotton Production. R.E. Frisbie, K.M. El-Zik, and L.T. Wilson (eds.). John Wiley and Sons, New York. Pp. 121-153.

Cooke, D. A., and I. J. Thomason. 1979. The relationship between population density of Heterodera schachtii, soil temperature, and sugarbeet yields. Journal of Nematology 11:124-128.

Duncan, L. W. and H. Ferris. 1983. Effects of Meloidogyne incognita on cotton and cowpeas in rotation. Proceedings of the Beltwide Cotton Production Research Conference: 22-26.

Ferris, H. 1984. Probability range in damage predictions as related to sampling decisions. Journal of Nematology 16:246-251.

Ferris, H. 1985. Population assessment and management strategies for plant-parasitic nematodes. Agricultural, Ecosystems and Environment 12(1984/85):285-299.

Ferris, H., D. A. Ball, L. W. Beem and L. A. Gudmundson. 1986. Using nematode count data in crop management decisions. California Agriculture 40:12-14.

Ferris, H., H. L. Carlson and B. B. Westerdahl. 1994. Nematode population changes under crop rotation sequences: consequences for potato production. Agronomy Journal 86:340-348.

Ferris, H., P. B. Goodell and M. V. McKenry. 1981. Sampling for nematodes. California Agriculture 35:13-15.

Goodell, P.B., M. A. McClure, P. A. Roberts, and S. H. Thomas 1997. Nematodes. In: Integrated Pest Management for Cotton in the Western Region of the United States. 2nd edition. Univ. of California Publ. No. 3305. Pp. 103-110.

Roberts, P.A. and G.D. Griffin. 1994. The economic feasibility of management alternatives. In: Quantifying Nematode Control. G.D. Griffin and P.A. Roberts (eds.). Western Regional Research Publication #149, Utah State University Press, Logan, UT. Pp. 23-49.

Roberts, P.A. and I.J. Thomason. 1981. Sugarbeet Pest Management: Nematodes. Univ. of California Special Publ. No. 3272. 32 pages.