Sensitivity of anastomosis groups in Rhizoctonia spp. inciting maize sheath blight to three fungicides in Shanxi Province

To clarify the sensitivity of the main anastomosis groups of Rhizoctonia spp. inciting maize sheath blight to flutolanil, thifluzamide, and pencycuron in Shanxi province, the EC₅₀ values of 268 Rhizoctonia spp. were determined by mycelium growth rate method, and sensitivity baselines were established. Additionally, the correlation between thifluzamide and other fungicides on inhibitory activities to Rhizoctonia spp. was analyzed. The results indicated that the anastomosis grops of R. solani AG-5 and R. zeae WAG-Z were the most sensitive to thifluzamide, followed by flutolanil, and least sensitive to pencycuron, and R. solani anastomosis subgroup AG-1-IA were the most sensitive to pencycuron, followed by thifluzamide, and least sensitive to flutolanil. After removing the outliers of EC₅₀ values using boxplot analysis, both AG-5 and WAG-Z exhibited a continuous unimodal distribution of sensitivity frequencies to the three fungicides, complying with a normal distribution. Therefore, the mean EC₅₀ values of 0.165, 0.048, and 2.500 μg/mL were established as the sensitivity baselines for AG-5 to flutolanil, thifluzamide, and pencycuron, respectively. Similarly, the mean EC₅₀ values of 0.518, 0.106, and 1.616 μg/mL were defined as the sensitivity baselines for WAG-Z to flutolanil, thifluzamide, and pencycuron, respectively. There was no observed correlation between thifluzamide and flutolanil, pencycuron, hexaconazole, or fludioxonil in terms of their inhibitory activity on AG-5 and WAG-Z. The results could serve as a valuable reference for the development of fungicide application strategies, monitoring and risk assessment of fungicide resistance for maize sheath blight in Shanxi Province, China.