Comparative toxicity of chlorantraniliprole and spinetoram against Spodoptera litura (Fabricius) under laboratory conditions

Abstract

Spodoptera litura (Fabricius) is a destructive polyphagous pest of pulse crops, including green gram (Vigna radiata (L.) R.Wilczek), causing severe defoliation and significant yield losses. Identifying insecticides with high toxicity and rapid action is essential for effective management of this pest. The present study evaluated the comparative toxicity of chlorantraniliprole and spinetoram against 11 day old larvae of S. litura under laboratory conditions. Larval bioassays were conducted using the leaf-dip method and mortality was recorded at 12, 24, 48 and 72 hr after treatment (HAT). Probit analysis was performed to estimate lethal concentrations (LC) and compare the relative toxicity of the two insecticides. The toxicity of both insecticides increased with exposure time, as indicated by a progressive decline in LC₅₀ values. Chlorantraniliprole consistently exhibited greater toxicity than spinetoram throughout the study. At 24 HAT, chlorantraniliprole exhibited a substantially lower LC (0.008 %) than spinetoram (0.064 %), indicating approximately 8-fold greater toxicity. The difference in toxicity gradually decreased with prolonged exposure and both insecticides exhibited an identical LC₅₀ value (0.002 %) at 72 HAT, resulting in high larval mortality. Overall, both insecticides were effective against S. litura larvae. However, chlorantraniliprole produced faster and greater toxic effects than spinetoram. These findings support the use of chlorantraniliprole as a rapid-acting insecticide and highlight the potential of both molecules for the integrated pest management (IPM) of S. litura in green gram.