Insecticidal Efficacy of Origanum compactum Essential Oils against Callosobruchus maculatus: A Sustainable Approach to Stored Legume Protection

Abstract

The infestation of stored legumes by Callosobruchus maculatus poses a critical threat to food security, leading to substantial post-harvest losses, reduced nutritional value, and compromised storage practices, ultimately affecting both economic stability and the availability of essential food resources. This study investigates the developmental cycle of C. maculatus and evaluates the insecticidal efficacy of Origanum compactum essential oils (EOs) using contact and inhalation methods. Laboratory experiments were conducted under controlled conditions at 26±1°C, 70±5% relative humidity, and a 14:10-hour light-dark photoperiod. The developmental cycle of C. maculatus was observed through dissection, while the insecticidal efficacy of O. compactum EOs was tested using contact and inhalation methods. The developmental cycle of C. maculatus chickpea seeds was approximately 30±2 days under controlled conditions (28°C, 75% RH). It comprised an egg stage (5 days), four larval instars (10 days), a pupal phase (9 days), and adult emergence (5 days). Oviposition peaked during the first three days and ceased by day seven, emphasizing rapid reproductive behavior. Inhalation tests with Origanum compactum essential oil achieved 100% mortality at 16µL after 72hours, confirming strong toxicity. Also, contact tests revealed 100% mortality at 16µL within 24hours, demonstrating rapid insecticidal efficacy. The findings demonstrate that O. compactum EOs are highly effective against C. maculatus, providing a promising eco-friendly alternative to synthetic pesticides.