Sensitivity and efficacy of boscalid, fluazinam, and thiophanate-methyl for white mold control in snap bean in New York

White mold (Sclerotinia sclerotiorum) of leguminous crops in New York is generally managed with preventive applications of fungicides. However, no research has been conducted during the last decade to assess the sensitivity of the S. sclerotiorum population to fungicides or compare their performance under field conditions. The sensitivity of S. sclerotiorum to boscalid, fluazinam, and thiophanate-methyl was assessed in 151 isolates from 15 fields across New York using an agar dilution method with discriminatory concentrations. In addition, the effective concentration at which mycelial growth is reduced by 50% (EC50) was estimated for one representative isolate from each field. The efficacy of commercial formulations of each fungicide on white mold incidence in plants and pods was also tested in two field trials (2015 and 2016). The EC50 values ranged from 0.068 to 0.219, 0.001 to 0.002, and 1.23 to 2.15 µg/ml for boscalid, fluazinam, and thiophanate-methyl, respectively. Evidence of resistance was not fou...