Abstract:

To explore the optimal control strategy for rice sheath blight and effectively manage its occurrence while reducing chemical pesticide usage, this study systematically evaluated rice cultivar resistance, biocontrol efficacy, and fungicide activity targeting Rhizoctonia solani. The results demonstrated that cultivars 'Yuandao 26', 'Zhengdao 22', 'Wanjing 608', and 'Xindao 18' exhibited consistent moderate resistance or higher to sheath blight across both 2022 and 2023 growing seasons; biocontrol strains 1340, BR-4, and Dw-1 showed superior control efficacy with inhibition rates of 76.7%, 53.4%, and 75.0% respectively; among chemical agents, fludioxonil, thifluzamide, epoxiconazole, and propiconazole demonstrated optimal fungicidal activity with EC₅₀ values of 0.07 mg/L, 0.17 mg/L, 0.24 mg/L, and 0.40 mg/L respectively. Resistance factors were calculated as 0.41×, 1.84×, 4.07×, and 0.65×, all below resistance risk thresholds. Therefore, selecting cultivars maintaining moderate resistance for consecutive years, applying biocontrol agents in low-disease-pressure fields, and utilizing high-efficacy/low-resistance-risk fungicides like fludioxonil in severely infected areas will achieve efficient management of rice sheath blight while minimizing chemical inputs.

Key words: rice sheath blight, disease resistant varieties, biocontrol bacteria, control effect, chemical agents, activity, fungicide resistance