Abstract:To try to seek and discover new antifungal activity from now available mature insect inhibitors, not only being able to expand their application ranges, but also being able to reduce the invest and time of developing new pesticides. We found the mycelial growth of Rhizoctonia solani AG-1IA was suppressed by insecticide hexaflumuron. By comparing the virulence of this chemical to R.solani AG-1IA on cultural medium PDA (in vitro) and on rice plant (in vivo), the toxicity of the chemical to this fungus was 4.1 times higher in vivo than in vitro. Stronger activities of β-1, 3-glucanase and total chitinase in the rice sheath were stimulated treated with 50μg/mL hexaflumuron after 7d and 14d, respectively. These results suggested that not only there is the direct toxicity of the pesticide against the pathogen but also defense reactions were triggered in rice plant after spraying it. Hexaflumuron will be a potential chemical which replaced Jinggangmycin because its effect on rice sheath blight in rice field was 88.6%.