Abstract:

To clarify the control effect of 1,2-Dibenzoyl-1-tert-butylhydrazine (RH-5849) against the Spodoptera exigua and to facilitate its application, this study conducted topical bioassays to evaluate the toxicity of RH-5849 on the 3^rd and 4^th instar larvae of S. exigua at concentrations of 250, 500, 1000, 2000 and 4000 mg/L. The results showed that RH-5849 significantly disrupted larval development and molting. The median lethal concentration (LC₅₀) was 1619.352 mg/L for 3^rd instar larvae after 96 h of exposure, and 634.610 mg/L for 4^th instar larvae after 96 h. In addition, RH-5849 treatment induced morphological abnormalities, characterized by a progressive change in larval body color from natural brown to pale green or white. Moreover, the higher the concentration of RH-5849, the more significant the colors change. The dose-dependent effect of RH-5849 on S. exigua is not significant. Considering both larval stage and RH-5849 concentration, 250 mg/L RH-5849 demonstrates superior efficacy against 3rd-instar larvae compared to other concentrations, while 500 mg/L RH-5849 was more effective against 4th-instar larvae. These findings provide foundational data for the potential integration of RH-5849 into S. exigua management strategies, either as a standalone treatment or in combination with other insecticides.

Key words: Spodoptera exigua, 1,2-Dibenzoyl-1-tert-butylhydrazine (RH-5849), topical application, toxicity determination, median lethal concentration (LC₅₀)