Bioactivity of cypress leaf powder (Cupressus macrocarpa) on cowpea weevil (Callosobruchus maculatus Fabr. Coleoptera: Bruchidae) and maize weevil (Sitophilus zeamais Motschulsky, Coleoptera: Curculionidae) in stored maize grains in Cameroon

Abstract

Cowpea weevil (Callosobruchus maculatus) and maize weevil (Sitophilus zeamais) are very destructive pests of cowpea and maize respectively. Synthetic chemicals have been used extensively to control these pests. The present study investigated the potential of cypress leaf (Cupressus macropcarpa) powder as a biological agent against these pests. Three doses (g) of cypress leaf powder (2, 5 and 10g) were exposed to 10 adult insects in triplicate and mortality was observed every 24hrs for 3days. A repellency test was also conducted in triplicate using 3 doses (g) (2, 5, and 10g) of cypress leaf powder. The experimental design was Completely Randomised Design (CRD). The experiments were conducted in a laboratory (28 ± 2 °C and 80 ± 10% RH) in the Farm house of the Faculty of Agriculture and Veterinary Medicine, University of Buea, Cameroon The results revealed that, the cypress leaf powder did not cause any significant mortality (p > 0.05) compared to the controlled for both insect pests. The repellency test revealed that the cypress leaf powder showed a very high potential as a repellent agent (p < 0.05) with up to 50-60% of both insect pests repelled just after 10mins of exposure to the smallest dose (2g). About 90% repellency was observed for both pests from the highest dose (10g) within 10mins of exposure making 10g a perfectly repellent dose. Our research supports strongly that cypress leaf powder has a strong repellency effect on both pests and little or no potential to cause significant mortality. Thus cypress leaf powder is a good candidate to incorporate in integrated pest management (IPM) programmes for control of cowpea and maize weevil in stored grains by poor-resourced farmers and store keepers in Cameroon and the world at large. Thus, appropriate technology transfer systems should be developed and passed on to poor-resources farmers to promote a direct preparation of indigenous pesticides at farm-house level.