Phytochemical Composition and Insecticidal Activity of Garlic (Allium sativum) Aqueous Extract against Callosobruchus maculatus (Cowpea Bruchid) in Zuru Central Market, Kebbi State, Nigeria

Abstract

This study evaluated the insecticidal potential of Allium sativum against the cowpea storage pest Callosobruchus maculatus at the Federal University of Agriculture, Zuru, Kebbi State, Nigeria. Cowpea is an important food crop but is highly vulnerable to infestation by C. maculatus, which causes significant post-harvest losses through seed damage, weight reduction, and loss of nutritional quality. Due to the limitations of synthetic insecticides, including toxicity, environmental pollution, and resistance development, botanical alternatives such as garlic have gained attention. Qualitative phytochemical screening of garlic extract revealed the presence of flavonoids, phenols, saponins, alkaloids, tannins, and organosulfur compounds, while steroids and glycosides were absent. Mortality of C. maculatus increased with concentration and exposure time. At 10 minutes, only the 30% concentration showed low mortality (11.1 ± 0.9%), while lower concentrations showed no effect. At 20 minutes, 20% and 30% concentrations produced high mortality. At 30 minutes, 20% and 30% concentrations achieved 100% mortality, while 10% showed high but incomplete mortality. Behavioural effects included restlessness, rapid movement, and knockdown responses, especially at higher concentrations. The study concludes that garlic extract exhibits strong insecticidal activity and supports its potential use as a sustainable botanical pesticide. Further research is recommended to optimise formulations and evaluate long-term storage effectiveness.