Grain Protectant Potential of Annona muricata and A. senegalensis against Cowpea Seed Bruchid Callosobruchus maculatus Fab. (Coleoptera: Bruchidae)

Annona muricata and Annona senegalensis powders were evaluated for their insecticidal potency against adult Callosobruchus maculatus. Toxicity test was conducted by contact bioassay at different concentrations of the treatment plants viz: 0.0 g, 0.5 g, 1.0 g, 2.0 g and 3.0 g was tested as well as their anti-ovipository activities, adult F1 progeny emergence suppression activities and anti-feedant activities which possibly result in the grain’ weight loss and grain damage was also tested. The results revealed that the treatment plants at all concentrations showed a significant (P>0.05) insecticidal potency, by recording higher mortality rates, suppression of egg laying and adult emergence, and reduced weight loss as well as grain damage when compared with the untreated control. The root bark of A. senegalensis at 3.0 g powder per 20 g grain had the higher mortality rate (98.5). The leaf and root bark powder of A. muricata at 3.0 g reduced oviposition minimum (1.4 respectively); leaf powder of A. muricata at 3.0 g powder per 20 g grain also reduced F1 generation emergence minimum (9.3) and root bark powder of A. muricata at 3.0 grams w/w reduced grain damage minimum (0.7). The results revealed that A. muricata at 3.0 g powder per 20 g grain for the leaf and root bark powders to be more effective in controlling C. maculatus than A. senegalensis. Therefore, it is recommended that farmers should put the practice of using Annona species, especially, A. muricata as an alternative to the dangerous and highly persistent chemical insecticides in the control of C. maculatus on stored cowpea.