Control effect and optimum sprayed period of chlorantraniliprole pesticide on Chilo suppressalis of early rice

Key Words：Chilo suppressalis, control efficacy, optimum control period, chlorantraniliprole, chlorantraniliprole thiametho, emamectin benzoate

Abstract：        The effectiveness and optimum spraying period of the three pesticides (chlorantraniliprole, chlorantraniliprole thiametho, and emamectin benzoate) were assessed with regard to the control of the striped rice borer Chilo suppressalis (Walker) on early rice in double rice-cropping seasons. The results indicate that chlorantraniliprole and chlorantraniliprole thiametho provided better and more prolonged control and a single application of these pesticides may effectively control multiple peaks of a striped rice borer epidemic. Spraying with 20% chlorantraniliprole (SC150 mL/hm²), 40% chlorantraniliprole thiametho (WDG120 g/hm2), and 2.15% emamectin benzoate (EC750mL/hm²)reduced the main peak of the larval epidemic by 94.7%, 91.2%, 91.0%, respectively after 8 days, and by 99%, 98%, 73.2% respectively, after 18 days . Chlorantraniliprole was most effective with 84.9% efficiency during the latter peak of sheath blight, and its 69.3% borer control was better than that achieved by chlorantraniliprole thiametho. However, emamectin benzoate had control efficacy of only 7.1%. The timing of spraying affected Chlorantraniliprole’s effectiveness; during the main peak of sheath blight, the optimum control period was at the peak of hatching followed by the 2nd stage larval peak. During the main peak of ovary blight, spraying was more effective from the peak of hatching to the 3rd larval stage. During the later sheath blight peak; an additional spray of the pesticide improved control efficiency. However, spraying too late during a massive early sheath blight epidemic resulted in depressed plant growth and reduced numbers of tillers as a result of early sheath blight. Therefore, it is recommended that chlorantraniliprole should be sprayed twice during the prominent and late peaks of egg hatching, in regions with heavy borer epidemics, but in regions with relatively light borer infestations spraying during the later peak of infestation may be sufficient.