Efficacy of Olive Oil and Chilli Pepper Powder in the Control of Cowpea Bruchid (Callosobruchus maculatus)

Abstract

Post-harvest losses caused by the cowpea bruchid (Callosobruchus maculatus) pose a significant threat to food security and economic stability in sub-Saharan Africa. This study investigated the insecticidal efficacy of two readily available botanicals—olive oil and chilli pepper (Capsicum spp.) powder—as sustainable alternatives to synthetic pesticides. A comprehensive laboratory bioassay was conducted, applying varying concentrations of each substance to C. maculatus over a 24-hour period under controlled hot season conditions (28-38°C). Concurrent phytochemical screening was performed to identify constituent bioactive compounds. Results demonstrated a concentration-dependent mortality response for both treatments. Olive oil proved significantly more effective (p < 0.05), achieving an overall mean mortality of 79.6% and an LC50 of 14.8%, compared to chilli pepper's 66.1% mortality and LC50 of 22.3 mg/ml. Phytochemical analysis revealed a broader spectrum of bioactive compounds in olive oil, including steroids and oxalates, which were absent in chilli pepper. The superior efficacy of olive oil is attributed to a dual mechanism of physical suffocation and synergistic biochemical toxicity. This research conclusively validates both botanicals, particularly olive oil, as highly effective, affordable, and eco-friendly biopesticides suitable for integration into stored product IPM strategies by smallholder farmers, directly contributing to reduced post-harvest losses and enhanced food security.