Abstract:
Objective Sensitivities of Rhizoctonia solani on rice to propiconazole and pyraclostrobin were determined for proper pesticide application on the disease control in Guizhou.
Method Mycelium growth rate was used as the criterion for testing the pesticide sensitivities of 52 strains of R. solani collected from 4 regions in the province.
Result The EC50 of propiconazole on the pathogens ranged from 0.058 μg·mL−1 to 2.381 μg·mL−1, averaging 0.422 μg·mL−1. That of pyraclostrobin were between 0.077 μg·mL−1 and 0.936 μg·mL−1, averaging 0.313 μg·mL−1. Strains of low resistance to the pesticides were found in Meitan area of the province with a resistance frequency of 16.7% on propiconazole and 13.3% on pyraclostrobin. A cluster analysis showed no significant correlation between the pesticide sensitivities and the geographical origins of the pathogens, nor between the two pesticides.
Conclusion A large number of the R. solani isolates in the study were highly sensitive to propiconazole and pyraclostrobin, and no apparent cross-resistance observed between the two fungicides. Hence, alternative application of them for disease control was deemed appropriate.