Insecticidal activity of Azadirachta indica A. Juss. and Jatropha curcas L. seed oils against cutworm Agrotis ipsilon (Hufnagel, 1766) (Lepidoptera: Noctuidae) on cabbage Brassica oleracea L.

Abstract

Cutworms Agrotis ipsilon (Hufnagel, 1766) (Lepidoptera: Noctuidae) are destructive pests of cabbage Brassica oleracea L. (Brassicaceae) and other cruciferous crops, causing severe yield losses by feeding on seedlings and young plants. Excessive use of synthetic pesticides has contributed to resistance development, environmental contamination, and health risks. In response, botanical insecticides have therefore gained increasing attention as sustainable pest control alternatives. This study evaluated the insecticidal efficacy of neem Azadirachta indica A. Juss. (Meliaceae) and physic nut Jatropha curcas L. (Euphorbiaceae) seed oils against cutworm larvae collected from cabbage farms in Jos North Local Government Area, Plateau State, Nigeria. Seed oils were extracted using Soxhlet extraction with n-hexane and evaluated using a leaf disc ingestion bioassay at concentrations of 15 %, 30 %, and 60 %. A synthetic insecticide (Moran® 30) and distilled water served as positive and negative controls respectively. Mortality was monitored for 72 h. Neem seed oil produced the highest mortality at 60 % concentration, achieving complete larval mortality within 24–48 h. Physic nut oil also exhibited notable insecticidal activity, but slightly lower efficacy when compared with neem oil. The statistical analysis revealed significant differences among treatments when comparing the botanical insecticides with the positive and negative control (P < 0.05). The study demonstrates that botanical oils can serve as effective alternatives to synthetic insecticides for cutworm management in cabbage production systems.