Effects of plant oils on oviposition preference and larval survivorship of Callosobruchus chinensis (Coleoptera: Bruchidae) on azuki bean [Vigna angularis]

The efficacy of four kinds of oils, neem, castor, sunflower and sesame, was evaluated for the control of infestation of stored azuki bean with Callosobruchus chinensis. Neem and sesame oil-treated beans were less preferred and oviposition of adults on these beans decreased. After three days of release, 100% adults were found dead on neem oil-treated beans and very few eggs were laid. Effects on the survival rate of immature beetles and percentage of seed weight loss were also recorded. Neem and sesame oils completely inhibited adult emergence and appeared to be most promising as a seed protectant against C. chinensis. The oil-specific activity and delay in larval development in oil-treated beans suggest that the protective properties involved chemical rather than physical factors.