Comparative study of the insecticidal efficacy of polyalthia longifolia (sonn.) Thwaites and acalypha wilkesiana (muell arg) powder on callosobruchus maculatus (f.) (coleoptera: bruchidae)

Concerns over the environmental impact of synthetic pesticides have shifted attention toward bioactive plant products for the control of stored-product insect pests. This laboratory study evaluated the insecticidal efficacy of Polyalthia longifolia and Acalypha wilkesiana leaf powders against the cowpea weevil (Callosobruchus maculatus). The study aimed to assess mortality effects, damage reduction and emergence inhibition. Four treatment concentrations (0%, 1%, 2%, and 3%) of each plant leaf powder were tested in a completely randomized design, with three replicates per treatment. Each replicate consisted of 100 g of sterilized cowpea grains. Results showed that A. wilkesiana caused the highest mortality rates of 30.23% at 3%, 23.35% at 2%, and 20.76% at 1%. P. longifolia exhibited mortality rates of 25.46% at 3%, 21.65% at 2%, and 16.65% at 1%. Both plant powders significantly increased mortality compared to the control (P < 0.05). Damage reduction was also significant, with A. wilkesiana reducing damage to 25.80% at 3% and P. longifolia to 32.35% at 3%. Additionally, emergence inhibition was notable, with A. wilkesiana suppressing F₁ progeny emergence by 78.74% at 3% and P. longifolia by 71.15% at 3%. The study concludes that both plants possess insecticidal properties capable of suppressing cowpea weevils, with A. wilkesiana demonstrating greater efficacy than P. longifolia. These findings highlight the potential of these plant-based powders for sustainable pest management, contributing to food security and environmental safety.