Evaluation of insecticidal properties of cuminum cyminum and piper nigrum essential oils against sitophilus zeamais

Abstract

Background and Objective: The increased and continuous use of synthetic insecticides develops risk of ozone depletion, neurotoxicity, carcinogenicity, teratogenicity and mutagenicity in non-target animal species and cross- and multi-resistance in insects. These possible consequences regarding human safety and possible environmental damage have diverted attention towards other alternatives especially the use of plant products in stored-grain insect pest management. In search of the environmentally safe green insecticides cumin (Cuminum cyminum) and black pepper (Piper nigrum) essential oils were evaluated for repellent, insecticidal, oviposition inhibitory and acetylcholine esterase enzyme inhibitory activities in maize weevil, (Sitophilus zeamais). Materials and Methods: Essential oils from cumin and black pepper were isolated by hydrodistillation method using Clevenger apparatus. Sitophilus zeamais (S. zeamais) adults were treated with both essential oils by fumigation and contact methods to determine the toxicity of essential oils. S. zeamais adults were treated with two sublethal concentrations of essential oils to determine its oviposition inhibitory and acetylcholine esterase enzyme (AChE) inhibitory activity (one-way ANOVA, p<0.01). Results: Both essential oils repelled S. zeamais adults significantly. In fumigation toxicity assay, median lethal concentrations (LC50) were 0.346 and 0.253 µL cm-3 air and 0.287 and 0.152 µL cm-3 air for C. cyminum and P. nigrum oils after 24 and 48 h exposure period respectively. In contact toxicity assay, LC50 were 0.246 and 0. 185 µL cm-2 area and 0.208 and 0.126 µL cm-2 area for C. cyminum and P. nigrum oils after 24 and 48 h exposure period respectively. Both essential oils were found to inhibit oviposition in S. zeamais adults when exposed to sub-lethal concentrations. Fumigation of S. zeamais adults with C. cyminum and P. nigrum oils inhibited AChE activity. Conclusion: C. cyminum and P. nigrum oils can be used as alternative in management of stored-grain insects.