Study of Toxicity of Selected Insecticides on Melon Fruit Fly, Zeugodacus cucurbitae (Coquillett)

The melon fruit fly Zeugodacus cucurbitae (Coquillett) is a major pest of cucurbitaceous crops, causing substantial economic losses through larval infestation and fruit damage. Although insecticides are used for its management, their effectiveness varies with the active ingredient, concentration and exposure duration. Therefore, identifying insecticides that induce rapid and high mortality is important for developing effective management strategies, including attract-and-kill systems. In this study, the oral toxicity of four insecticides was evaluated against adult male Z. cucurbitae under laboratory conditions. Malathion 50 EC was tested at 0.50, 1.00 and 2.00 mL L⁻¹, deltamethrin 2.8 EC and emamectin benzoate 1.9 EC at 1.00 and 2.00 mL L⁻¹ each, and chlorantraniliprole 18.5 SC at 0.15, 0.30, 0.60 and 1.20 mL L⁻¹. Mortality was recorded at 1, 2, 6, 12, 24 and 48 h, and the effects of concentration and exposure time were assessed using factorial analysis of variance. Malathion 50 EC exhibited the highest toxicity, causing 95.00 per cent mortality at 2.00 mL L⁻¹ after 6 h and complete mortality at all tested concentrations by 24 h. Deltamethrin 2.8 EC caused 85.00–95.00 per cent mortality at 24 h, while Abbott-corrected mortality at 48 h ranged from 74.44 to 89.44 per cent for emamectin benzoate 1.9 EC and from 53.33 to 74.44 per cent for chlorantraniliprole 18.5 SC. Concentration and exposure time significantly influenced mortality for all four insecticides, whereas their interaction was non-significant. Malathion 50 EC at 2.00 mL L⁻¹ was selected for further evaluation in an attract-and-kill system against Z. cucurbitae.