In present study, the morphological and physiological characteristics of Sclerotinia sclerotiorum (Lib.) de Bary to a novel succinate dehydrogenase inhibitor (SDHI) fungicide penthiopyrad has been reported. The baseline sensitivity of S. sclerotiorum to penthiopyrad was determined using 119 strains by inhibition of mycelial growth. The median effective concentration (EC₅₀) values for penthiopyrad ranged from 0.0096 to 0.2606 μg/ml, and the mean value was 0.0578 (±0.0626) μg/ml. After 1 μg/ml penthiopyrad treatment, mycelia of S. sclerotiorum strains showed increased apical branching and were denser compared with control, and cell membrane permeability significantly increased. In addition, glycerol content, oxalic acid (OA), and exopolysaccharide (EPS) content decreased markedly and mycelial respiration was distinctly inhibited. The number and dry weight of sclerotia significantly decreased after being treated with 2 μg/ml penthiopyrad. Penthiopyrad exhibited both protective and curative activity on the detached rapeseed leaves. Importantly, the above results will provide us more information on penthiopyrad for management of diseases caused by S. sclerotiorum and increase our understanding of action of penthiopyrad against S. sclerotiorum.

Keywords: Sclerotinia sclerotiorum; activity; penthiopyrad; sensitivity distribution.