Sensitivity of Colletotrichum gloeosporioides causing grape anthracnose to three sterol demethylation inhibitor (DMI) fungicides

The sensitivity,cross sensitivity,the relationship of sensitivity and fitness of 57 isolates of Colletotrichum gloeosporioides (Penz.) Penz.& Sacc.,collected from main grape production districts of Yunnan Province,to diniconazole,myclobutanil and prochloraz were tested.The results indicated that the EC50 values of all isolates to prochloraz ranged from 0.01 mg/L to 1.58 mg/L,lower than that to diniconazole (0.05-25.45 mg/L) and myclobutanil (0.49-192.93 mg/L).Based on frequency distribution of EC50 values of C.gloeosporioides populations to the three sterol demethylation inhibitor (DMI) fungicides,it was revealed that sensitivity of some isolates to diniconazole and myclobutanil had significantly decreased,but almost all isolates still kept higher sensitivity to prochloraz.The sensitivity correlation analysis for the isolates to the three DMI fungicides showed that the sensitivity of isolates to diniconazole and myclobutanil had remarkable correlation,however there were no correlation between prochloraz and diniconazole (or myclobutanil).There was no significant difference between low sensitive isolates and sensitive isolates on pathogenicity and colony growth,which indicated that low sensitive isolates still had relatively high survival fitness.