1. Nematode Thresholds and Damage Levels
Howard Ferris and Philip Roberts
Nematology Workgroup Meeting
March, 2005

2. Some Constraints to Early Adoption
Sources of Data
Ferris et al, 1970s and 1980s
Roberts et al, 1980s
Cooke and Thomason, 1970s
Some Constraints to Early Adoption
Availability of inexpensive nematicides
Development of resistant varieties in some crops
Publication of thresholds in arcane format

3. Some of those involved….
Dan Ball
Larry Duncan
Pete Goodell
Joe Noling
Diane Alston
Sally Schneider
Lance Beem

4. Thresholds by field plot
South Coast Field Station
USDA Shafter
Tulelake

5. Thresholds by transect
Imperial and Coachella Valleys
Ventura County
Tulare County

6. 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

7. Case Study on Cotton Cultivar Soil Location (T)olerance Z m SJ2
loamy sand
south SJV 65
0.998
0.55
Deltapine
imperial 50
0.9972
0.65
SJ2, SJ5, SJ-C1
l. sand/s. loam 55
0.999
0.48
average (all) 57
0.56
average (SJV) 60
0.9985
0.52
SJ2(-FOV)
sandy loam
0.9966
0.54
SJ2(+FOV)
0.9847
0.38

8. Case Study on Cotton 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 5 15 27 41
Deltapine
imperial 19 7 16 26 34
SJ2, SJ5, SJ-C1
l. sand/s. loam 21 4 10 37
average (all) 22 6 40
average (SJV) 23 12 24
SJ2(-FOV)
sandy loam 45
SJ2(+FOV) 42 59 62

9. Damage Function Parameters for Selected Crops
(T)olerance Z m
Bell Pepper 65
0.9978
0.87
Cantaloupe 10
0.9972
0.40
Carrot
0.99
0.6
Chile Pepper 39
0.9934
0.70
Cotton
57.5
0.9976
Cowpea 22
0.9816
0.96
Potato 18
0.49
Snapbean 14
0.57
Squash
0.9898
Sugarbeet
0.9955
0.89
Sweetpotato
0.47
Tomato
41.8

10. Thresholds and Expected Yield Loss
Meloidogyne incognita, J2/250 cc soil; adjusted for extraction efficiency
Expected % yield loss at different preplant nematode densities
Crop
Threshold 1 2 5 10 20 50
100
200
Bell Pepper 25 8
Cantaloupe 4 3 7 17 30 46
Carrot 9 16 29 37 40
Chile Pepper 15 14 24
Cotton 22 6 27
Cowpea 52
Potato 34 47 51
Snapbean 18
Squash 12 23 41 74 93
Sugarbeet
Sweetpotato 43
Tomato

11. Expected Damage
Meloidogyne chitwoodi; summer crop potato; Klamath Basin
Fall 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 7 8 12 15 18 25

12. Thresholds and Expected Yield Loss
Heterodera schachtii, eggs/100g soil
Sugarbeets
Cultivar
Soil
Location
(T)olerance Z m
US-H9
clay
Imperial
100
loam
SJV/Idaho
300
Expected % yield loss at different preplant nematode densities
Cultivar
Soil
Location
Threshold 50
100
200
500
1000
US-H9
clay
Imperial 11 37 64
loam
SJV/Idaho
300 5 15

13. Some References
Benedict, J.H., K.M. El-Zik, L.R. Oliver, P.A. Roberts, and L.T. Wilson 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
Cooke, D. A., and I. J. Thomason The relationship between population density of Heterodera schachtii, soil temperature, and sugarbeet yields. Journal of Nematology 11:
Duncan, L. W. and H. Ferris Effects of Meloidogyne incognita on cotton and cowpeas in rotation. Proceedings of the Beltwide Cotton Production Research Conference:
Ferris, H Probability range in damage predictions as related to sampling decisions. Journal of Nematology 16:
Ferris, H Population assessment and management strategies for plant-parasitic nematodes. Agricultural, Ecosystems and Environment 12(1984/85):
Ferris, H., D. A. Ball, L. W. Beem and L. A. Gudmundson Using nematode count data in crop management decisions. California Agriculture 40:12-14.
Ferris, H., H. L. Carlson and B. B. Westerdahl Nematode population changes under crop rotation sequences: consequences for potato production. Agronomy Journal 86:
Ferris, H., P. B. Goodell and M. V. McKenry Sampling for nematodes. California Agriculture 35:13-15.
Goodell, P.B., M. A. McClure, P. A. Roberts, and S. H. Thomas Nematodes. In: Integrated Pest Management for Cotton in the Western Region of the United States. 2nd edition. Univ. of California Publ. No Pp
Roberts, P.A. and G.D. Griffin 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
Roberts, P.A. and I.J. Thomason Sugarbeet Pest Management: Nematodes. Univ. of California Special Publ. No pages.