Study of insecticidal properties of garlic, allium sativum (alliaceae) and bel, aegle marmelos (rutaceae) essential oils against sitophilus zeamais L. (coleoptera: curculionidae)

Abstract

Background and Objectives: The continuous use of synthetic pesticides has increased the risk of ozone depletion, neurotoxicity, carcinogenicity, teratogenicity and mutagenic effects among non-target species and cross-resistance and multi-resistance in insects. These have created increased public awareness on human safety and possible environmental damage diverting attention towards other alternatives especially the use of plant products in stored-grain insect pest management. In the present study, essential oils of Allium sativum (A. sativum) and Aegle marmelos (A. marmelos) have been evaluated for their repellent, insecticidal, anti-ovipositional and acetylcholine esterase inhibitory activities against maize weevil, Sitophilus zeamais (S. zeamais). Materials and Methods: Garlic, Allium sativum and bel, Aegle marmelos essential oils have been isolated and evaluated for repellent, insecticidal, oviposition inhibitory and acetyl cholinesterase enzyme inhibitory activities in maize weevil, Sitophilus zeamais. One-way analysis of variance (ANOVA, p<0.01), correlation and linear regression analysis were used for data analysis. Results: In repellency assay, both essential oils showed repellent activity against S. zeamais adults. These essential oils caused toxicity in S. zeamais adults when applied by fumigation and contact methods. In fumigation toxicity assay, median lethal concentrations (LC50) recorded were 0.297 and 0.22 µL cmG3 air, 0.312 and 0.184 µL cmG3 air of A. sativum and A. marmelos oils after 24 and 48 h exposure of S. zeamais adults, respectively. In contact toxicity assay, median lethal concentrations (LC50) were found 0.208 and 0.116 µL cmG2 area and 0.227, 0.146 6,37 µL cmG2 area of A. sativum and A. marmelos oils after 24 and 48 h exposure of S. zeamais adults, respectively. Essential oils of A. sativum and A. marmelos oils were found to inhibit progeny production by inhibiting oviposition in S. zeamais adults when exposed to sub-lethal concentrations. Fumigation of S. zeamais with A. sativum and A. marmelos oils caused neurotoxicity by inhibiting acetylcholine esterase enzyme (AchE) activity. Conclusion: A. sativum and A. marmelos oils can be used as alternative in management of stored-grain insects.