Biotic Stress and Yield Loss

in HLAI, RI, and RUE, accounting for differences in net assimilation, biomass, andyield of the crop. With these known variables, data from different locations and yearscan be collectively analyzed and summarized. The major difficulty with this conceptis the length of time necessary to measure LAI data. 68 To help alleviate this problemin the future, limited LAI sampling could be integrated with remote sensing to savetime and resources.This approach should help us to better understand how single or multiple bioticstresses affect the net biomass production of a crop. This would allow the creation ofmodels that would predict crop yields throughout the season, and be site specific,given historic environmental parameters. As the growing season progresses and theenvironmental conditions are updated into the model along with the relative RI andRUE, growth stage, predicted weather conditions, presence of pathogen, price ofcommodity, and cost of sprays, pest management decisions would be made as economicthresholds are reached.REFERENCES1. Gaunt, R. E., The relationship between plant disease severity and yield, Annu. Rev.Phytopathol., 33, 119, 1995.2. James, W. C., Assessment of plant diseases and losses, Annu. Rev. Phytopathol., 12, 27,1974.3. Chester, K. S., Plant disease losses: their appraisal and interpretation, Plant Dis. Rep.Suppl. 193, 189, 1950.4. Cook, R. J., Use of the term “crop loss,” Plant Dis., 69, 95, 1985.5. Stevenson, W. S., Management of early and late blight, in Potato Health Management,Rowe, R. C., Ed., APS Press, St. Paul, MN, 1993, chap. 16.6. Johnson, K. B., and Teng, P. S., Coupling a disease progress model for early blight to amodel of potato growth, Phytopathology, 80, 416, 1990.7. Backman, P. A., and Jacobi, J. C., Thresholds for plant-disease management, in EconomicThresholds for Integrated Pest Management, Higley, L. G., and Pedigo, L. P., Eds.,University of Nebraska Press, Lincoln, 1996, chap. 8.8. Nutter, F. W., Jr., Teng, P. S., and Royer, M. H., Terms and concepts for yield, crop lossesand disease thresholds, Plant Dis., 77, 211, 1993.9. Nutter, F. W., Jr., Disease severity assessment training, in Exercises in Plant DiseaseEpidemiology, Francl, L. J., and Neher, D. A., Eds., APS Press, St. Paul, MN, 1997,chap. 1.10. Tomerlin, J. R., and Howell, T. A., DISTRAIN: A computer program for training peopleto estimate disease severity on cereal leaves, Plant Dis., 72, 455, 1988.11. Madden, L. V., and Nutter, F. W., Jr., Modeling crop losses at the field scale, Can. J. PlantPathol., 17, 124, 1995.12. Backman, P. A., and Crawford, M. A., Relationship between yield loss and severity ofearly and late leafspot diseases of peanut, Phytopathology, 74, 1101, 1984.13. Shaner, G., and Finney, R. E., The effect of nitrogen fertilization on the expression of slowmildewing resistance in Knox wheat, Phytopathology, 67, 1051, 1977.14. Broscious, S. C., Pataky, J. K., and Kirby, H. W., Quantitative relationships between yieldand foliar diseases of alfalfa, Phytopathology, 77, 887, 1987.