Sensitivity of Bipolaris maydis to propiconazole, diniconazole and prochloraz in Fujian province

The sensitivities of Bipolaris maydis to propiconazole, diniconazole and prochloraz were determined by measuring the mycelial growth on the fungicide-amended media using 185 isolates collected from 15 counties of Fujian province. The results indicated that 50% effective concentration(EC50) values of all isolates to propiconazole, diniconazole and prochloraz ranged from 0.0186 to 7.779, 0.0416 to 22.32 and 0.0053 to 7.930μg/mL, respectively. The results of the frequency analysis revealed that low sensitivity subcolony had been discovered in the tested isolates. The mean EC50 values of(0.5199±0.0284),(0.4079±0.0204) and(0.3818±0.0202) μg/mL for most isolates showed a unimodal curve distribution, which was treated as the sensitivity baseline of B. maydis to propiconazole, diniconazole and prochloraz, respectively. 15.14%, 20.00% and 17.30% of the isolates exhibited resistance to propiconazole, diniconazole and prochloraz, respectively. And the EC50 values of the highest resistant isolates were 14.96, 54.71 and 20.77 folds of the sensitivity baseline, respectively. There was obvious cross resistance among the 3 kinds of fungicides. Especially, the correlation efficient existed between propiconazole and diniconazole is the highest(r=0.8662). The results provided a theoretical basis for the efficient application of fungicides in the control of corn southern leaf blight in the field.