Evaluation of protectant ability of Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus in cowpea, Vigna unguiculata L. (Walp.) was carried out in the laboratory at ambient temperature of 28 ± 2°C and 70 ± 5% relative humidity. Extracts from wood ash, leaf, stem and root bark were tested at different concentrations of 0, 1, 2, 3, 4 and 5%. One hundred per cent mortality of adult beetles was achieved at all concentrations within 72 h of treatment with extracts except in wood ash at 1% concentration, but they were significantly different (p < 0.05) from the controls. All the extracts were still able to cause high beetle mortality after one, two and three months of cowpea storage at high concentrations (4 and 5%) except wood ash, although there was a slight decrease in mortality during the period of storage. All the extracts significantly (p < 0.05) reduced oviposition and adult emergence of C. maculatus when compared with the controls although the reduction was higher at 5% concentration than others. Adult beetle emergence was completely prevented at higher concentrations (4 and 5%) except in wood ash. Both oviposition and adult emergence increased during the months of storage probably because of the slight reduction in the effectiveness of the extracts. The root bark extract was much more effective in reducing oviposition and adult emergence than others throughout the period of storage. The plant extracts of N. laevis was able to protect the cowpea seeds from damage and prevent weight loss. Cowpea seed damage and weight loss was significantly more (p < 0.05) in the controls than other for the three-month duration probably because of the more adult emergence. The extracts from N. laevis did not adversely affect the germination of the protected seeds and seed germination ranged from 86.7 to 100%. It has been shown in this study that the extracts of N. laevis were effective against C. maculatus in cowpea although the root bark extract seemed to be the most effective while the wood ash extract was least effective. Their effectiveness, however, slightly decreased during the period of storage. N. laevis could be incorporated into pest management of stored cowpeas since the products are ecologically safe.

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Powders and extracts of Azadirachta indica, Zanthoxylum zanthoxyloides, Anacardium occidentale and Moringa oleifera were assessed in the laboratory at ambient temperature of 28±2 o C and relative humidity of 75±5% for their insecticidal activity against Sitophilus oryzae, Oryzaephilus mercator and Ryzopertha dominica infesting paddy rice. The powders of these plants were tested against these insects at 0.4g, 0.6g, 0.8g and 1g/50g of paddy while the extracts were tested at 2%, 4%, 6% and 8% concentrations. Both the powders and extracts of these botanicals evoked a high mortality effect on the insects. Moreover, both the extracts and powders of A. indica and Z. zanthoxyloides showed greater insecticidal bustle than the powders and extracts of A. occidentale and M. oleifera as they both achieved 100% insect mortality within a short period after treatment. The extracts of these plants were also able to prevent the emergence of adult insects. S. oryzae and R. dominica were more affected with all the powders and extracts of these botanicals than O. mercator which was more vulnerable to the extracts and powders of Z. zanthoxyloides than other botanicals. Moreover, all the plants used showed a greater insecticidal effect and could be integrated into pest management system.

This study was conducted under laboratory conditions at temperature of 28±2 o C and relative humidity 75±5% to investigate the entomocidal flurry of Newbouldia laevis against Sitophilus oryzae and Sitophilus zeamais infesting maize grain in storage. The powders of stem and root of N. laevis were prepared at 0.1, 0.2, 0.3, 0.4 and 0.5g dosages, while their extracts were prepared at 1, 2, 3, 4 and 5% concentrations. The control experiments were also set up. None of the powders of stem and root of this plant was able to achieve complete mortality of the two insects within 96h of application, except for the root powder which was able to achieve 100% mortality of S. oryzae at 0.5g dosage only. Only the root extract at 4% was able to achieve complete weevils mortality within 96h and its effect was significantly different (p<0.05) from the extracts of the stem except at 4 and 5% concentration of stem extract. The fiducial limits showed that a lower concentration of root extract was needed to cause 50% mortality in S. zeamais (0.00-1.64 %) when compared to the concentration needed for S. oryzae (0.10-1.72 %). Both the stem and root extracts of the plant were more effective than their powders. The powders and the extracts of this plant either reduced or prevented the emergence of adult weevils and inhibit the developmental period of the insects. The powders and the extracts of N. laevis also reduced or prevented the weight loss of the treated maize grains. Therefore, with the result obtained in this research, both the powder and extract of N. laevis root and stem could go a long way in the quest of providing alternative wherewithal to the use of chemical insecticides for protecting maize grain in storage. Root extract of N. laevis could, however, offer more protection against S. oryzae and S. zeamais infesting maize grain than its stem extracts.