Ocimum gratissimum essential oil and modified montmorillonite clay, a means of controlling insect pests in stored products

The insecticidal properties of formulations based on Ocimum gratissimum essential oil and montmorillonite clay have been improved after modifications of the clay. Insecticidal tests have been conducted against the maize weevil Sitophilus zeamais. The mortality of S. zeamais decreased from 100% to 95%, 87% and 0% after 7 days, respectively, for the essential oil adsorbed on modified clay, unmodified clay or used without adsorbent. The formulation prepared with unmodified clay completely lost insecticidal activity after 30 days, whereas the formulation with modified clay lost about 60% of its full insecticidal potency in the same time. The insecticidal effects of the essential oil persisted for about 7, 45 and 80 days respectively for crude essential oil; after adsorption on unmodified and after adsorption on modified clay. The findings suggest that formulations based on essential oils adsorbed on modified clays can be considered as alternatives to synthetic insecticides for use in stored product protection. (c) 2012 Elsevier Ltd. All rights reserved.