Comparison of Moringa oleifera Lam seed powder and actellic dust (2%) in the control of Callosobruchus maculatus F. (Coleoptera : Bruchidae) on stored cowpea and their effects on nutritional and organoleptic characteristics

Horse-radish (Moringa oleifera Lam) seed powders were evaluated in the laboratory relative to a conventional storage chemical, actellic 2% dust (Pirimiphos-methyl) as protectants of stored cowpea against the cowpea bruchid, Callosobruchus maculatus F. M. oleifera was tested at four rates (2.5, 5.0 and 10.0 g/ 100 g seed including a control, i. e. 0.0 g). Actellic dust was applied at the rate of 1.0, 2.0, 3.0 g/ 100 g seed and 0.0 g/ 100 g seed as control. Data were collected over a seven month period on percentage mortality, oviposition, adult emergence and seed damage. The seed damage data were used to estimate the weevil perforation index (WPI). All data were analyzed for variance at P <= 0.05. M. oleifera performed comparatively well with actellic dust and the efficacy was dose-related. Actellic dust at the lowest rate inflicted adult mortality of 90-100% in the first 48 h after treatment and prevented oviposition by between 95-100% over the first five months of storage compared to the control. M. oleifera at the highest rate of 10.0 g per 100 g seed caused mortality upto 63.3% in 48 h and also reduced oviposition by between 50-80.0%, while adult emergence and seed damage were reduced between 35.4 and 90.3% with a WPI of between 3.3 and 40.0%. Proximate analysis and germination test experiments showed that the plant product and actellic dust increased the moisture and crude fibre content, decreased the crude protein content but had no significant effect on the viability of the stored cowpea seeds. Organoleptic tests showed that the treatment materials had no significant negative effect on taste, odour, texture, appearance and overall acceptability of cooked cowpea seeds after six months of storage. The results generally indicated that the powdered form of M. oleifera seed at the highest rates (i. e. 5.0 and 10.0 g/ 100 g seed) gave significant protection of cowpea seeds against the cowpea bruchid comparable to actellic dust when applied prophylactically.