Deterrent effects of citrus peel oils on oviposition and adult emergence of thecowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Oil extracts of the fruit peels of five citrus species namely Citrus tangerina, C. limonium, C. paradisi, C. aurantifolia and C. sinensis were investigated for their effect on oviposition and adult emergence of the cowpea weevil, Callosobruchus maculatus on cowpea seeds, Vigna unguiculata. The oils were extracted by hydrodistilation and applied on the cowpea seeds in concentration series of 5.5ml and 2.75ml. The results indicated that a significant (P < 0.05) reduction in oviposition and adult emergence of C. maculatus were recorded in all the treatments with citrus oil compared to the control. Oviposition deterrence in the weevils was highest in treatments with C. sinensis (72 - 79%) and lowest with C. tangerina (62 - 68%). Reduction in emergence in the treatments with the essential oils ranged between 89 and 98%, oils of C. paradisi and C. sinensis recorded the highest effect (98%) while C. tangerina recorded the lowest effect (89%). The effectiveness of the citrus peel oils in deterring oviposition and reducing emergence of the cowpea bruchid could be explored and used as biocide in the management of this cowpea pest