Effect of plant oil treatments against Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) on stored maize

The effect of plant oil treatments extracted from Khaya ivorensis and Azadirachta indica was evaluated on adult maize weevils Sitophilus zeamais reared on maize grain. Four replicates of each treatment oils were constituted at 0% (control untreated), 1 ml, 2 ml, and 3 ml doses. Each of the pytochemical oil and the synthetic chemical (Daksh- Dichlorvos 100% EC w/v) was introduced into experimental jars (300 cm3) at graded levels, before 20 g of clean maize grain was incorporated. The treatment oils were separated from the grains with perforated white paper, before 10 newly emerged adult S. zeamais was added to the experimental jars including the control (untreated) experiment, which contain 20 g of maize grain but no treatment was added. The plant oils were evaluated for their toxic effect on S. zeamais, oviposition, F1 progeny emergence, grain damage and weight loss. Data collected were analyzed using ANOVA. The means were separated using LSD at P>0.05.The results revealed that treatment oils were toxic to the maize weevils when compared with the control (untreated) experiment. Among the plants, essential oil of K. ivorensis significantly (P>0.05) suppressed egg laying, F1 progeny emergence and grain damage. Therefore, the essential oil of K. ivorensis and A. indica is useful in the control of S. zeamais.