Laboratory evaluation of plant powders against the maize weevil, Sitophilus zeamais (Coleoptera: Curculionidae), in stored sorghum

Sorghum, (Sorghum bicolor L. Moench) one of the oldest cultivated cereals and a major staple food for millions of people in many tropical and subtropical regions, is highly vulnerable to postharvest losses caused by storage pests such as the maize weevil, Sitophilus zeamais Motschulsk. Although the insecticidal effects of several botanical powders against S. zeamais have been previously reported, evidences specific to stored sorghum remains limited. The present study confirmed and comparatively evaluated the insecticidal efficacy of three plant-based powders: Phytolacca dodecandra L'Her, Nicotiana tabacum L., and Millettia ferruginea Hochst. against adult maize weevils under laboratory conditions. Treatments were applied with varying concentrations (0.4, 0.6, 0.8 and 1.0g/100g) of each botanical powder, while untreated and 5% malathion dust were used as controls. Adult mortality, progeny emergence, grain damage, and weight losses were recorded over a 15 day period. Results showed that P. dodecandra caused the highest adult mortality (96.6 ± 5.7), followed by N. tabacum (83.3 ± 0.0), and M. ferruginea (53.3 ± 3.8). All botanicals powder significantly reduced grain damage, and weight loss compared to the untreated control. These findings confirm the effectiveness of these botanicals in stored sorghum and highlight their potential relevance as locally available, eco-friendly alternatives to synthetic insecticides in Ethiopian postharvest pest management. Further research is needed under farm-level storage conditions to validate their practical applicability.