Insecticidal Potential of Citrus sinensis (L.), Citrus limon (L.) and Piper guineense (Schumach. & Thonn.) against Sitophilus zeamais (Motsch ) Infection in Zea mays (L.) (Maize)

Abstract

Stored product insect pests are largely responsible for post-harvest losses in Sub-Saharan Africa. Chemical insecticides are usually used for control but are hazardous to health and the environment. One of such destructive pests is the maize weevil Sitophilus zeamais. The use of botanicals in pest management against weevils are safe alternatives. This study investigated the insecticidal properties of powders of Citrus sinensis (orange) peel CSP, Citrus limon (lemon) peel, CLP and Piper guineense (black pepper) seed, PGSP applied singly, and in 1:1 combinations. These were evaluated for the control of S. zeamais in stored maize grains under ambient temperature and relative humidity of 29.77oC±0.38 and 55%±1.80, respectively, in the laboratory at the Department of Zoology, University of Ibadan, Nigeria. There were 6 treatments groups, each with ten unsexed adults of S. zeamais which were introduced into 50 g of maize, 3 groups were treated with CSP, CLP and PGSP and 3 groups with the combinations: CSP and CLP,1:1; CSP and PGSP, 1:1; CLP and PGSP, 1:1 at 0.5g, 1.0g and 1.5g per 50g of maize grains respectively. The period of exposure was 90 days. Permethrin was used as control. At 1.5/50g concentration, numbers of live insects present in all treatments were evaluated. Single applications of CSP and CLP, had no significant difference p≥ 0.05 compared with the untreated group. However, the single application of PGSP and all three combined applications had significantly fewer insects p≤ 0.05. This confirms that PGSP and the treatment combinations have insecticidal properties.