Detection of sensitivity of grape anthracnose to thiophanate methyl, tebuconazole and kresoxim-methyl

Seventy eight isolates of Colletotrichum gloeosporioides collected from grapes in Hangzhou,Shengzhou and Jiaxing of Zhejiang Province were characterized for sensitivity to thiophanate methyl,tebuconazole and kresoxim-methyl by mycelial growth method.The results showed that the isolates had developed serious resistance to benzimidazole fungicides with resistance frequency of 51.3%,which belong to high level resistance.The EC50 values of tebuconazole,a demethylation inhibitor to the isolates ranged from 0.04 to 21.56 μg/mL with a mean value of 1.63 μg/mL.Among them,the isolate of L-58 showed the least sensitivity with EC50 value of 21.6 μg/mL.SHAM,a specific inhibitor of alternative oxidase,showed notable synergistic interaction with kresoxim-methyl against mycelial growth of C.gloeosporioides.In the absence of SHAM,the medium effective concentrations (EC50Q) inhibiting growth rate of the tested population by kresoxim-methyl ranged from 0.03 to 436.55 μg/mL, with an average value of 27.77 μg/mL.In the presence of 50 μg/mL SHAM,the EC50(EC50Q+S) ranged from 0.01 to15.20 μg/mL,with an average value of 4.40 μg/mL.The factor value (F=EC50Q/EC50Q+S) for the impact of alternative respiration on sensitivity to kresoxim-methyl ranged from 0 to 155.47,with an average of 20.09.