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Disease Detection and Losses

Relationship of Bacterial Leaf Blight Severity to Grain Yield of Rice. A. P. K. Reddy, Plant pathologist, All India Co-ordinated Rice Improvement Project (AICRIP) Hyderabad-30 A.P. India; D. R. MacKenzie(2), D. I. Rouse(3), and A. V. Rao(4). (2)(3)Associate professor and graduate assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; (4)Statistician, AICRIP. Phytopathology 69:967-969. Accepted for publication 22 March 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-967.

Field experiments were conducted to evaluate the relationship between severity of bacterial leaf blight (BLB) on rice and on yields. Epidemics of BLB with different disease progress curves were encouraged by manipulating the initial dates and frequencies of subsequent inoculations, the use of a bactericide, and selection of rice cultivars thought to differ in disease reaction to the causal organism, Xanthomonas oryzae. Late season epidemics (ie, initiated after flowering) had no measurable effect on grain yield or yield components. Epidemics that began before panicle initiation significantly reduced grain yield, panicle fertility, and kernel weight. The discovery of a significant, linear relationship between BLB severity at the soft dough stage of plant growth and grain yield allowed the construction of a critical point model to predict BLB-associated crop losses.