The bioactivity of Alstonia boonei De Wild (Apocyanaceae) against Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) in stored cowpea seeds was evaluated in the laboratory by admixing leaf, stem bark and root powders of A. boonei with cowpea seeds at ambient temperature of 28+2⁰C and 70+5% relative humidity. The powders were incorporated into 20g of cowpea seeds, Vigna unguiculata at 0.0% (control) 2.5%, 5.0%, 12.5% and 25.0% (w/w) concentration. The ability of the plant powders to protect cowpea seeds was assessed in terms of mortality rates after 24 - 96 hours post treatment, oviposition and adult emergence, percentage weight loss and damage after the first filial generation (F₁). All the tested plant part powders significantly (P<0.05) reduce the longevity of adult C. maculatus on treated cowpea seeds. From the study, the plant powders could be ranked in order of effectiveness thus; stem bark > leaf > root. Alstonia boonei can be used as biopesticide against C. maculatus and its incorporation into traditional storage pest management is strongly recommended.

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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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Susceptibility studies keep farmers informed, and enhance breeding programmes' testing against infestation and damage by stored product pests. Therefore, the susceptibility of 20 elite maize varieties toSitophilus zeamaisinfestation was investigated in the laboratory at 32.7 °C ambient temperature and 70.4% relative humidity. The varieties tested were obtained from the Maize Breeding Units of International Institute of Tropical Agriculture (IITA), and Institute of Agricultural Research and Training (IAR&amp;T), both in Ibadan, Nigeria. Susceptibility was assessed, using as indices, weevil mortality and survival rates, percentage grain damage, percentage grain weight loss, weight of grain powder, weevil development time, and number of emerged adults. The susceptibility index was determined post-infestation at 56 days using Dobie's formula and at 90 days from a new formula derived from Dobie's formula. Susceptible varieties produced significantly (P≤ 0.05) high numbers of F1and F2progeny, and had significantly (P≤ 0.05) low weevil mortality and early first weevil emergence. Grain damage and loss increased with storage duration. There was no visible damage to varieties 2000SYNEE-WSTR and TZBRELD3C5 at 56 days post-infestation. At 90 days, the two varieties had the lowest percentage grain damage, percentage weight loss, and weight of grain powder. The index of susceptibility at F2progeny showed that the resistant varieties decreased in number from 17 (85%) to 13 (65%) and the moderately resistant varieties increased from 2 (10%) to 6 (30%). This suggests the effect of prolonged storage duration on the inherent ability of varieties to resist weevil attack. Variety PVASYN3F2 was susceptible. The factors conferring high resistance to 2000SYNEE-WSTR and TZBRELD3C5 should be investigated. They should be promoted to controlS. zeamaisinfestation and damage in stored maize.