Effects of selective insecticides on Zeugodacus cucurbitae (Diptera: Tephritidae) reared on bitter gourd under laboratory conditions

Chemical control has traditionally served as the principal method for managing pests in cucurbit crops; however, the urgent need to mitigate environmental risks and ensure food safety has driven the exploration of sustainable alternatives. The present study was carried out during Kharif 2024 at the Entomology Laboratory, ICAR–Indian Institute of Vegetable Research, Varanasi, to evaluate the influence of insecticides from diverse chemical groups on the biology and morphometrics of the melon fruit fly, Zeugodacus cucurbitae. The test insecticides included chlorantraniliprole, cyantraniliprole, thiamethoxam, imidacloprid, indoxacarb and azadirachtin. Their effects were examined on developmental duration, adult longevity, oviposition period, fecundity and body dimensions. The results revealed that anthranilic diamides exerted the most pronounced impact. Chlorantraniliprole and cyantraniliprole markedly prolonged developmental time (female longevity of 37.23 and 33.76 days, respectively, versus 30.82 days in control) and azadirachtin, as well as cyantraniliprole, significantly suppressed fecundity (52.40 and 54.26 eggs compared with 81.40 in control). Among concentrations, imidacloprid at 16 ppm (45.33 eggs) and azadirachtin at 16 ppm (50.48 eggs) per female adult caused the greatest reduction in fecundity, whereas indoxacarb at 4 ppm showed minimal effect (79.78 eggs). Morphometric traits were similarly affected, with chlorantraniliprole reducing larval length (1st instar 1.49 mm and 3rd instar 9.15 mm against 1.85 mm and 10.05 mm in control) and adult female width (13.55-14.41 mm vs 15.79 mm in control). Indoxacarb responses closely resembled control, while azadirachtin produced intermediate suppression. Overall, the findings indicate that anthranilic diamides, particularly chlorantraniliprole and cyantraniliprole, along with the botanically derived azadirachtin, are promising candidates for disrupting the growth and reproduction of Z. cucurbitae. When used in rotation or integrated with botanicals and ecological strategies, these insecticides can form a sustainable foundation for melon fruit fly management.