EntomoToxicity of Xylopia aethiopica and Aframomum melegueta in Suppressing Oviposition and Adult Emergence of Callasobruchus maculatus (Fabricus) (Coleoptera: Chrysomelidae) Infesting Stored Cowpea Seeds

The cowpea beetle, Callosobruchus maculatus (Fabricus) (Coleoptera: Chrysomelidae), is a major pest of stored cowpea militating against food security in developing nations. The comparative study of Xylopia aethiopica and Aframomum melegueta powder in respect to their phytochemical and insecticidal properties against C. maculatus was carried out using a Complete Randomized Design (CRD) with five treatments (0, 1.0, 1.5, 2.0 and 2.5g/20g cowpea seeds corresponding to 0.0, 0.05, 0.075, 0.1 and 0.13% v/w) replicated thrice under ambient laboratory condition (28±2°C temperature and 75±5% relative humidity). The phytochemical screening showed the presence of flavonoids, saponins, tannins, cardiac glycoside in both plants, while alkaloids was present in A. melegueta and absent in X. aethiopica. The mortality of C. maculatus increased gradually with exposure time and dosage of the plant powders. X. aethiopica caused 75.15% adult mortality and A. meleguta exerted 85% mortality at 120 hrs post infestation. Maximum oviposition deterrent activity was observed with X. aethiopica (54.26%) compared to A. melegueta (51.32%). Conclusively, both plants showed highly useful bioactivity against C. maculatus in suppressing oviposition and adult emergence and, therefore, can be used in formulating ecofriendly herbal insecticides.