The use of solar energy and citrus peel powder to control cowpea beetle Callosobruchus

Abstract

This work aimed to evaluate the efficiency of different natural promising techniques in controlling cowpea beetle Callosobruchus maculatus the main pest of different legume seeds. To achieve this, the potential of solar energy and citrus peel powder to suppress cowpea beetle population were investigated. First, effect of solar energy was evaluated using a metal-box heater at different exposure times (5- 20 min). The box heater resulted in 100% of adult beetles mortality within 15 min (54°C), and totally suppressed the beetle population when immature stages were exposed to sun for 20 min (58- 64°C). The adult beetle was the most sensitive stage where as the second larval instar was the most tolerant one. The pupal stage when exposed to sub-lethal dose of solar energy produced adults with some morphological abnormalities. Solar energy treatment had no negative effect on germination of cowpea seeds, but interestingly, the germination was even better. Secondly, different concentrations of lemon and orange peel powders were applied: 0.01, 0.03, 0.075 and 0.1 gm/gm of cowpea seeds. Lemon peel powder was more effective than orange peel powder and had higher repellency activity. The (LC50s) were determined to be 0.025 and 0.086 gm/gm cowpea seeds for adult beetles after 3 d of treatment with lemon and orange peel powders, respectively. The effect of citrus powder on the adult insect cuticle and spiracles was also investigated using scanning electron microscopy