Diagrammatic scale for assessment the severity of Cercospora leaf blight on soybean (Glycine max) leaflets

Introduction. Cercospora leaf blight (CLB) caused by kikuchii is an endemic soybean crop disease in Argentina. Objective. To develop and validate a scale to quantify the severity of CLB leaflets (Glycine max) for evaluation foliar fungicides cultivar trials. Materials methods. A diagrammatic assess on was developed. The based 50 leaflets. different levels were determined according Weber-Fechner’s stimulus-response law. proposed included 1, 4.5, 17.5, 50, 82.2, 95, 99 %. validation performed 23 raters (3 experienced 20 inexperienced) who assessed with without use scale. Results. results from three more precise than those obtained inexperienced raters. improved visual interpretation raters, estimated values close actual values. When used estimate leaflets, they accurate having determination coefficients (R2) between 0.74 0.91. According absolute errors, greatest deviation observed -2.49 2.46. However, these deviations not significantly population average. speed process evaluations we also propose scales grades. Conclusions. can be assessment fungicide trials cultivars. showed specificity assessing (CFB)