Site-specific risk factors of white mould epidemics in bean (Phaseolus vulgaris) in Tasmania, Australia

In Tasmania, Australia, if more than 5% of bean pods are affected by white mould (Sclerotinia sclerotiorum) shipments may be rejected by the processor. This standard dictates prophylactic fungicide application over flowering, although in some instances treatment may not be warranted because oflow disease risk. Surveys were conducted to identify relationships among edaphic factors, weather variables, and production practices associated with white mould. Correlations were found between disease incidence and the number of apothecia, fungicide timing, and mean minimum air temperature in the 10- and 30-day periods preceding harvest. Significant differences in disease incidence also were detected among cultivars and bean canopy densities. A nonparametric discriminant analysis model based on the predictor variables ofmean minimum air temperature in the 10- and 30-day periods before harvest, cultivar, bean canopy density, and fungicide application correctly predicted presence of white mould on pods in 77% of bean fields. Several factors that can be manipulated to reduce disease risks were identified.