Efficacy of Kigelia africana Lam. (Benth.) leaf and stem bark ethanolic extracts on adult cowpea seed beetle, [Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae)] affecting stored cowpea seeds (Vigna unguiculata)
2020
Obembe, Olusola Michael | Ojo, Durojaye Olanrewaju | Ileke, Kayode David
Callosobruchus maculatus is the most damaging insect pest of stored cowpea (Vigna unguiculata) seeds in Nigeria. Thus, this present research work was put in place to assess the insecticidal activities of the extracts obtained from the leaf and stem bark of Kigelia africana (Lam.) Benth against the cowpea seed beetle, C. maculatus. The parameters that were assessed were adult mortality, oviposition and adult emergence of C. maculatus. The experiments were conducted under laboratory conditions of 28±2 °C temperature and 75 ± 5% relative humidity. The extracts were applied at dosages of 0.3, 0.6, 0.9 and 1.2 mL per 20 g of cowpea seeds. The two extracts of K. africana were found to be toxic to the survival of the C. maculatus. However, the extract obtained from the leaf was more potent to the beetle than the extract obtained from the stem bark of the same plant. The two extracts also reduced ovipositipon and completely suppressed adult emergence at the highest dose of 1.2 mL per 50 g of cowpea seeds. The results obtained in the present research work showed that the two extracts of K. africana were effective in suppressing the population of the infamous stored pest of cowpea seed beetle, C. maculatus and could therefore be recommended to replace the harmful synthetic chemical insecticides in protecting cowpea seeds in storage.
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