Insecticide-induced mortality and toxicity in two insect pests of sweet gourd

Abstract: Sweet gourd (Cucurbita moschata) is a popular and nutritious vegetable widely grown in tropical and subtropical regions, including Bangladesh during both winter and summer seasons. The insects of red pumpkin beetle (Aulacophora foveicollis) and epilachna beetle (Epilachna dodecastigma) are potential pests that adversely affect sweet gourd production in Bangladesh. Chemical insecticides are considered as the primary and most widely used tools for managing these pests in sweet gourd production. In this study, the mortality, weight reduction, and toxicity effects of six insecticides-AC Mix 55 EC, Damdama 440 EC, Decis 2.5 EC, Phyphanon 57 EC, Imitaf 20 SL, and Ripcord 10 EC along with an untreated control were evaluated against red pumpkin beetle and epilachna beetle under laboratory conditions. Results showed that among the insecticides, AC Mix 55 EC, Damdama 440 EC, and Decis 2.5 EC caused significant mortality of the beetles at 24, 48, and 72 hours after treatment with their recommended doses. The recommended dose of AC Mix 55 EC caused 100% mortality of red pumpkin beetle and 93.3% mortality of epilachna beetle at 24 h after treatment, while Damdama 440 EC caused 91.0% and 93.3% mortality at 48 h, and Decis 2.5 EC caused 96.7% and 91.7% mortality at 72 h, respectively. AC Mix 55 EC caused the highest weight reduction of red pumpkin beetle (43.1%), followed by Decis 2.5 EC (36.9%) and Damdama 440 EC (29.8%). For epilachna beetle, the highest weight reduction was also caused by AC Mix 55 EC (39.9%), followed by Decis 2.5 EC (33.6%) and Imitaf 20 SL (29.9%). Probit analysis confirmed that Decis 2.5 EC was the most toxic insecticide against the beetles, with the lowest LC₅₀ (26.3 ppm, 26.5 ppm) and LC₉₅ (70.6 ppm, 62.0 ppm), followed by Ripcord 10 EC (LC₅₀ = 104.5 ppm and 98.8 ppm, LC₉₅ = 385.4 ppm and 422.3 ppm) and AC Mix 55 EC (LC₅₀ = 172.2 ppm and 350.5ppm, LC₉₅ = 387.3 ppm and 481.1 ppm). E S H 

Keywords: Aulacophora foveicollis, Cucurbita moschata, Epilachna dodecastigma, mortality, toxicity