Patterns of Rhizoctonia Foliar Blight on Soybean and Effect of Aggregation on Disease Development

Abstract

Each of six soybean fields with a history of Rhizoctonia foliar blight was divided into 0.75-×0.75-m quadrats. Diseased leaves in each quadrat were initially counted at soybean growth stage V8-V11. At soybean growth stage R4, disease incidence in each quadrat was assessed. Lloyd's index of patchiness (LIP) of diseased leaves ranged from 1.56 to 4.54 at the first rating. At the second disease rating, LIP of disease incidence for each plot ranged from 1.32 to 2.15, indicating a decrease in disease aggregation (except for 1987 Lake Arthur). Cluster size was examined using paired-quadrat variance analysis (...)