Biology and eco-friendly management of cowpea weevil (Callosobruchus maculatus) in pea

Abstract

A study was conducted in the Entomology laboratory of Gauradaha Agriculture Campus at Jhapa district of Nepal to observe the biology and evaluate the efficacy of botanicals against cowpea weevil (Callosobruchus maculatus), which causes serious seed losses of leguminous crops during storage. The cowpea weevil was observed to complete its life cycle with egg-larva-pupal stages lasting 7-18-5 days respectively and the adult lived for 16 days. A completely randomized design was laid with 3 replications of seven treatments; neem (leaf powder) mugwort (leaf powder), sweet flag (rhizome powder), turmeric (rhizome powder), black pepper (seed powder), clove (seed powder), and lemongrass (leaf powder), each 10gm kg^-1 pea seeds and compared to an untreated control. Adult mortality and grain damage were recorded for 14 days after treatment at 2 days’ interval. Significant (p ≤ 0.001) differences in the mortality of weevils and grain damage were observed among the treatments. Black pepper showed the highest efficacy with full mortality within 2 days and least grain damage (1.94%) followed by clove (3.33%) and sweet flag (6.67%) reaching full mortality within 4 days, lemongrass (17.50%) and turmeric (14.16%) reached 100% mortality within 12 and 14 days, while neem and mugwort showed very slow effectiveness causing 90% and 86.66% mortality in 14 days and significant grain damage. However, untreated pea seeds suffered severe grain damage (35.83%) and provided conditions for the development of new generation weevils. The results depicted that the use of botanicals provide protection against grain damage, demonstrating their potential as an eco-friendly measure for sustainable storage pest management in legumes.