Susceptivity of Sclerotinia sclerotiorum to Triazole Fungicides at Different Growth Stages

The inhibition bioactivities on mycelial growth of 6 triazole fungicides and 4 others against Sclerotinia sclerotiorum(Lib.)de Bary were determined by mycelial growth rate method in lab,and examed their effects on sclerotium formation and sclerotium germination.The results showed that thiophanate-methyl had the weakest inhibitory effect on mycelial growth,its EC50 value was 65.75 μg/mL.Hexaconazole and tebuconazole had more significant inhibitory effects,their EC50 values were 0.09 μg/mL and 0.16 μg/mL, relative toxicity coefficient to thiophanate-methyl were 763.7 and 423.4 times,respectively. Secondary were propiconazol, mvclobutanil and flusilazole, which relative toxicities ranging from 137.3 to 286.6 times of thiophanate-methyl. Triadimefon had lower inhibition, its relative toxicity was 20.6 times of thiophanate-methyl.The EC50 values of procymidone and Junduqing were more than 10 μg/mL.At the concentration of EC50,all the tested fungicides did not affect the number of sclerotium.But the weight of sclerotium fell more than 70% after treated with triazole fungicides. All the triazole fungicides had no effect on the germination of sclerotium below the concentration of 10 μg/mL.