Pesticidal efficacy of Gmelina arborea Roxb Powders and Ethanol extracts on Bean Bruchids, Callosobruchus maculatus (Coleoptera: Chrysomelidae).

Abstract

Cowpea has become an easy source of protein worldwide and especially in Africa, yet most of the yields are lost as a result of infestation by pest especially Callosobruchus maculatus. The pesticidal efficacy of Gmelina arborea was tested on C. maculatus. The experiment was conducted using a Complete Randomized Block Design. G. arborea leaf powder showed a mean mortality of 4.25±1.35, 2.75±1.29 and 1.92±1.38 when 10g 5g and 2.50g of the powder was applied and a percentage mortality of 85%, 55% and 38.33% respectively. Stem bark powder showed a mean mortality of 1.33±1.16, 2.08±1.31 and 2.92±1.38 when 2.50g, 5.00g and 10.00g was applied and a percentage mortality of 26.67%, 41.67% and 58.33% respectively. The leaf ethanol extract showed a mean mortality of 4.67±2.27, 3.67±1.72 and 2.83±2.17 at 500mg, 250mg and 125mg concentrations and a mortality percentage of 93.33%, 73.33% and 56.67% respectively while the G. arborea stem bark ethanol extract revealed a mean mortality of 2.75±1.29, 3.58±1.83 and 4.17±1.95 at 125mg, 258mg and 500mg concentrations with percentage mortality of 55%, 71.67% and 83% respectively. The pesticidal efficacy between the leaf and stem bark ethanol extracts showed that p ≥ 0.05 for all concentrations used and between the powders, p ≥ 0.05 at 5.00g and p ≤ 0.05 at 2.50g and 10.00g. In view of these findings both G. arborea leaf and stem bark extracts and powders can be used to effectively control infestation of cowpea by C. maculatus.