Contact toxicity of some fixed plant oils and stabilized natural pyrethrum extracts against adult maize weevils (Sitophilus zeamais Motschulsky)

The contact toxicity of some selected fixed plant oils and stabilized natural pyrethrum (Chrysanthemum cinerariaefolium) blends against adult maize weevils (Sitophilus zeamais) were investigated. Natural pyrethrum extract was stabilized against ultraviolet (UV) light by blending with fixed oils extracted from Azadirachta indica A. Juss (neem tree), Thevetia peruviana (yellow oleander) and Gossypium hirsutum L. (cotton) seeds. Cottonseed oil had the highest stabilization effect on the pyrethrum blend exposed to UV light of 366 nm. The results indicated that the natural pyrethrum extract blended with cottonseed oil was the most potent against maize weevils and that the potency was concentration-time dependent. Cottonseed and neem seed oils enhanced the stabilization of the natural pyrethrum insecticide.