Toxicity of spinosad to the pulse beetle, Callosobruchus chinensis (Coleoptera: Bruchidae) and its parasitoid, Dinarmus basalis (Hymenoptera: Pteromalidae)

Abstract

Toxicity of Spinosad 45SC against adults of pulse beetle, Callosobruchus chinensis and its hymenopteran parasitoid, Dinarmus basalis was determined using dry film contact toxicity method under laboratory conditions. Spinosad was found to have contact toxicity against C. chinensis and the median lethal concentration (LC50) values at 24, 48 and 72 hours posttreatment were 51.05, 11.99 and 1.92 ppm, respectively. Contact toxicity of spinosad to D. basalis was higher with LC50 values of 0.130, 0.062 and 0.015 ppm at 24, 48 and 72 hours post-treatment, respectively. Field evaluation of Spinosad 45SC in mungbean and urdbean revealed that the insecticide was effective in reducing pod (82.9 to 84.9% reduction over control) and seed (76.5 to 78.1% reduction over control) damage due to the pulse beetle and comparable with conventional insecticide Dichlorvos 76EC (81.8 to 90.2% and 82.4 to 84.4% reduction in pod and seed damage, respectively). The present results provide informative data on susceptibility of pulse beetle and its parasitoid to spinosad for developing efficient pest management programs.