Comparative efficacy of moringa, neem and lemon grass leaf powders in the control of bean beetle (Callosobruchus maculatus Fab.) infesting cowpea (Vigna unguiculata L. Walp)

Insecticidal property of neem, moringa and lemon grass leaf powders were tested on C. maculatus feeding on stored cowpea in laboratory at 31.90C and relative humidity of 15.5 %. Eleven treatments were used, at three levels for each plant (1.0, 1.5 and 2.0/50g’. In addition, permethrin was used as positive control and untreated sample as negative control. The treatments were arranged in a completely randomized design (CRD) replicated three times. Four pairs of insects were introduced into each treatment and mortality was recorded for ten days. The mortality was 100% on the sixth day in seeds treated with moringa and neem leaf powders. Highest weight loss was in the negative control 1.18 g (2.37%) compared to 0.48g (0.95%) in the neem. Toxicity and feeding deterrent effect of all the three treatments were dose dependent, i.e. it increases as the dose increases. Therefore, moringa and neem leaf powders were effective protectants of C. maculatus against cowpea. It is recommended that 1g of the moringa and neem be used, i.e. 2.0 % per 50g of cowpea.