Sensitivity of Australian Sclerotinia sclerotiorum isolates from bean fields to boscalid

Abstract

White mould caused by Sclerotinia sclerotiorum is one of the most damaging diseases of bean worldwide. High incidence of white mould can lead to complete crop loss through rejection by processors. Since 2004, in Australia, white mould is managed by the prophylactic application of the fungicide, boscalid during flowering. The sensitivity of S. sclerotiorum isolates (n =150) was tested using a mycelial growth assay. The effective concentration of boscalid required to reduce mycelial growth by 50% (EC50) was calculated using probit analysis. The frequency distribution of EC50 values was unimodal and similar to that of 11 non-exposed isolates collected from other crops or obtained from culture collections. No evidence of resistance or reduced sensitivity was found within the tested S. sclerotiorum population from Australian bean fields. This study provides valuable baseline data for monitoring changes in sensitivity to this fungicide.