Comparative efficacy of eight insecticide–acaricides against Tetranychus urticae Koch (Acari: Tetranychidae) and their residual impact on Coccinella septempunctata (L.) (Coleoptera: Coccinellidae)

The efficacy of eight insecticides and acaricides against Tetranychus urticae Koch (Acari: Tetranychidae) on Lablab purpureus (L.) and their residual effects on Coccinella septempunctata (Linnaeus) (Coleoptera: Coccinellidae) were evaluated under laboratory and potted plant conditions. In laboratory bioassays, abamectin and fenpropathrin caused 100% adult mite mortality within 4 h, whereas spiromesifen achieved 100% egg mortality. On potted plants, most pesticides significantly reduced T. urticae populations, with population reduction exceeding 90% by 7 days after treatment for all compounds except fenpropathrin. Fresh residues of emamectin benzoate and lambda-cyhalothrin caused the highest mortality (>75%) of C. septempunctata, followed by abamectin (66.7%), whereas toxicity declined progressively with residue age. Spiromesifen exhibited consistently low toxicity throughout the study. Under the present experimental conditions, spiromesifen provided the most favourable balance between sustained mite suppression and low residual toxicity to C. septempunctata. In contrast, abamectin may remain IPM compatible if predator exposure is minimised. Field validation is nevertheless required.