Abstract:

Sensitivity of 157 isolates of Botrytis cinerea collected from different regions of Hebei and Shandong provinces to difenoconazole was tested by measuring mycelial growth rate. EC50 values for 86 isolates from the areas where the difenoconazole have never been used before, were （0.3958±0.3485）μg/mL, ranging from 0.0135μg/mL to 1.2832μg/mL.The data could be used as baseline sensitivity of B. cinerea to difenoconazole. The results of monitoring showed that low resistant isolates to difenoconazole in B. cinerea occurred in collected areas, 9.5% low resistant isolates existed,but moderate resistant or high resistant isolates were not detected. It was found that no positively-correlated cross resistance relationship exists between difenoconazole and other fungicides with different action mechanism, by analysing the correlation logarithms of that EC50 values between difenoconazole and other fungicides that pyrimethanil, procymidone, carbendazim, diethofencarb and iprodione to different isolates of B. cinerea to the base 10.