Post-harvest bruchid richness and residual activity of pirimiphos-methyl on Callosobruchus maculatus F. infested pigeon pea (Cajanus cajan L. Millsp.) in storage

The residual activity of actellic dust (pirimiphos-methyl) on Callosobruchus maculatus F. and the fieldto-store bruchid richness of pigeon pea grains were studied at Nsukka, Nigeria. Results of the bruchid richness study showed that there was no emergence or infestation of bruchids from both the treated and untreated grains six months post harvest. Assessment of the residual activity of pirimiphos-methyl on C. maculatus six months post treatment revealed that although C. maculatus could not be controlled completely, its developmental potential and extent of grain damage were drastically reduced, which showed the continued activity of the pesticide six months post treatment. Incremental doses of actellic dust produced residual effects which significantly (