VIEW ARTICLE

Disease Control and Pest Management

Predicting Yield Losses in Corn from Southern Corn Leaf Blight. L. V. Gregory, Graduate Student, Department of Plant Pathology, The Pennslyvania State University, University Park, PA 16802; J. E. Ayers(2), and R. R. Nelson(3). (2)(3)Associate Professor, and Evan Pugh Professor, respectively, Department of Plant Pathology, The Pennslyvania State University, University Park, PA 16802. Phytopathology 68:517-521. Accepted for publication 29 August 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-517.

The effect of southern corn leaf blight caused by Helminthosporium maydis race T on corn in Texas male-sterile cytoplasm was investigated in the field in 1975 and 1976. Losses in yield of grain due to infection initiated late in the season were 9.7 to 11.7%. There was no significant difference (P=0.05) between yield in the delayed-inoculation treatment and controls in 1975 but there was a significant difference in 1976. Losses observed in treatments inoculated prior to anthesis were about 30%. Regression analysis was used to determine the relationship of percent yield loss and disease severities recorded at different stages in the growth of the crop. The best regression equation was derived from disease severities assessed at the dough stage in each year. Regression coefficients were 0.69 in 1975 and 0.70 in 1976 (R² = 86.3 and 87.0% respectively). Values for y-intercepts for these equations were not significantly different from zero (P = 0.05). Various transformations and multiple regression techniques were attempted but they did not enhance precision in the analysis. A generalized equation to predict yield loss was presented; ý = 0.69x_d; where ý is the percent yield loss and x_d is the percent diseased tissue at the dough stage. A method to estimate losses from disease assessments made prior to the dough stage using projected disease severities is presented.