Sensitivity of Sclerotinia sclerotiorum and its two biocontrol agents, Ulocladium atrum and Coniothyrium minitans, to boscalid and benomyl.

Studies were conducted to determine the effect of the fungicides boscalid and benomyl on spore germination and mycelial growth of the pathogen Sclerotinia sclerotiorum and its biocontrol agents, Ulocladium atrum and Coniothyrium minitans. Mycelial growth of all three fungi was sensitive to boscalid, whereas S. sclerotiorum and C. minitans were sensitive to benomyl at all the concentrations (10 to 4000 μg a.i./mL) tested, and U. atrum was sensitive to benomyl at higher concentrations (1000 μg a.i./mL or greater) but tolerant at lower concentrations. A similar trend was observed with respect to conidial germination, with the threshold level for U. atrum sensitivity to benomyl being 100 μg a.i./mL. The ecological implications of prophylactic use of broad-spectrum fungicides such as boscalid in combination with biocontrol agents are discussed.