Relation between web-blight disease and common bean yield

Abstract

The disease-yield relationship was studied in web-blight (Thanatephorus cucumeris Frank.) of common beans (Phaseolus vulgaris L.) under humid tropic conditions of Transamazon region. Data obtained from 24 different epidemics regulated by the application of fungicidal sprays were utilized. Three methods were tested for relating disease severities to grain yield: 1. critical-point method, 2. multiple-point method, 3. area under disease progress curve. There was no correlation between disease severities at vegetative growth stage and yield. Pod-filling stage was identified as critical for relating disease to grain yield in the cultivar Rico-23. The results further demonstrated that the loss in yield could be determined with reasonable accuracy utilizing the critical-point model.