ABSTRACT

Laboratory studies were conducted at the Crop Science Laboratory of Michael Okpaia University of Agriculture, Umudike, Nigeria and at the Behavioural and Chemical Ecology Department of International Centre of Insect Physiology and Ecology Nairobi, Kenya to determine the efficacy of sonic plant powders, extracts and their essential oils for Sitop hi/us :eamais control in stored niaize grains. The relative effectiveness of selected plant powders for control of S. zeainais was investigated. Also the efficacy of different concentrations of P. guineense powder was studied. Effect of particle size on effectiveness of P. guineense against S. zeamais was also investigated. Mixtures of P. guilleense and C'ap.siciwi trutescens powders were also evaluated for grain protection against the maize weevil. Extracts of P. guineense seed with five different extractants were compared for their effectiveness in S. zeamais control. Also, the contact toxicity and repellent properties of the extracts were assessed. The effects of plant extracts on the basic food components of' treated maize were evaluated. The identity ofa total o123 constituent compounds of the essential oils of the 2 plants was confirmed and their relative proportion determined. lhe bioactivity of essential oils extracted by hydro distillation from leaves of fer,ioiii, amygda/uici and fruits ofXi/opia aetiopica using Clavenger apparatus was assessed under laboratory conditions at 30 0E' 65 ±2% and 12h: 12h light: (lark regimes against S. zeainais in maize grains. The effect of treatments on grain weight loss, insect mortality and progeny production was assessed. The constituent compounds of the essential oils were identified through Gas Chromatography (GC), Gas Chromatography- Mass Spectrometry (GC-MS) and GC- Co injection with the authentic standards. The results showed that P. guineense powder was the most effective in S. zeanzais control as it showed a significantly (P < 0.05 SNK) higher percentage mortality (78.9) as well as xiv reduced number of adult emergence than the other plant powders. The treatment of 0.3 g powder/20 g maize weight/weight proved to be the most effective for S. zeamais control. Finer particles (600 l.tm) of the plant powder showed significantly greater effectiveness in maize weevil control that compared favourably with the synthetic chemical, pirimiphos methyl. Mixtures of 80% P. guineense and 20% C. frufescens gave the best protection against S. zearnais. Acetonic extract of P. guineense seed caused significant mortality o1 the S. zeaniais (P