Toxicity of Four Essential Oils Against Two Insect Pests of Stored Grains, Rhyzopertha dominica (Coleoptera: Bostrychidae) and Sitophilus oryzae (Coleoptera: Curculionidae)

Abstract

The biological activity of essential oils extracted from four plants of the Lamiaceae family (Lavandula angustifolia Lawrence, 1989 (= L. officinalis Linnaeus), Mentha piperita Linnaeus, 1753, Ocimum basilicum Linnaeus, 1753 and Origanum compactum Bentham) was evaluated on adults of Rhyzopertha dominica Fabricius 1792 (Coleoptera: Bostrychidae) and Sitophilus oryzae Linnaeus, 1763 (Coleoptera: Curculionidae) using fumigation and repellency tests carried out at four doses and different exposure times, under laboratory conditions. The results obtained show that the four essential oils are often more toxic to R. dominica than to S. oryzae. LC50 varied between 15.14 and 18.49 µl/l of air for R. dominica, and between 33.51 and 50.27 µl/l of air for S. oryzae. The LT50 values ranged from 8 to 27 h for R. dominica and between 161 and 601 h for S. oryzae at a concentration of 20 µl/l of air. The oil of O. basilicum caused, after 96 h of fumigation at a concentration of 20 µl/l air/20 g of durum wheat, Triticum durum, 100 % mortality rates for R. dominica and 41 ± 13.87 % for S. oryzae. Oils of O. compactum and O. basilicum were the most active against R. dominica and S. oryzae, with repellency rates of 82 % and 60.5 %, respectively.