Evaluation of extracts of neem (Azadirachta indica A. Juss) for the control of some stored product pests

Laboratory investigations on the activity of neem leaf and seed extracts in water or methylated spirit on Callosobruchus maculatus, Sitophilus oryzae and Cylas puncticollis were made at 27 ± 2°C and 65 ± 5% r.h.. Field trials were conducted to determine their effectiveness as protectants of cowpeas and maize in storage at 28 ± 4°C and 82 ± 7% r.h for 5 months.

The results showed that the effectiveness of neem is affected by differences in insect behaviour. The extracts were more active as suppressants of C. maculatus than Sitophilus spp; there was no effect on C. puncticollis. All of the extracts tested resulted in a significant reduction in oviposition, % egg hatch and % adult emergence in C. maculatus and in adult emergence of Sitophilus.

Field trials showed that the extracts mostly gave good protection to cowpea against C. maculatus for 5 months, but only moderate protection to maize against S. zeamais. Seed extracts were more effective than leaf extracts.