Insecticidal Effect of Citrus Aurantifolia and Senna Spectabilis Leaf Powder and Methanol Extracts Against Two Major Storage Pests of Maize

Abstract

Botanicals have proven to be safer and more sustainable alternatives to synthetic insecticides in reducing postharvest losses caused by storage insect pests. With limited information on the insecticidal efficacy of Citrus aurantifolia and Senna spectabilis, this study aims to evaluate their effectiveness against Prostephanus truncatus and Sitophilus zeamais, contributing to sustainable grain protection. Laboratory and field studies were conducted at the Entomology laboratory and the University of Ghana School Farm, respectively. In both studies, maize grains were treated with methanol and powders of C. aurantifolia and S. spectabilis at 5% and 10%. Actellic DustÒ applied to maize grains at 0.06% wt/wt served as a positive control, and untreated grains as a negative control. The experimental units were arranged in a Completely Randomized Design with four replications. Phytochemical analysis was performed for both botanicals. The results revealed that the leaves of the botanicals contained bioactive compounds, such as alkaloids, flavonoids, phenolics, and tannins. Both powders and methanol extracts of the botanicals (5 and 10%) significantly reduced the survivorship and emergence of the storage pests, as well as the weight loss they caused under laboratory conditions. However, only the methanol extracts remained consistently effective under field conditions, significantly reducing grain damage, with powders being less reliable under practical storage conditions. These findings highlight the potential of methanol extracts of C. aurantifolia and S. spectabilis as effective protectants for stored maize. Future studies should emphasize evaluating the safety and cost-effectiveness of these botanicals to support sustainable grain protection to achieve zero hunger.