Mentha pulegium, Mentha suaveolens subsp. timija, Lavandula mairei, and Artemisia mesatlantica Essential Oils: Laboratory Screening for Biological Control Against Red Palm Weevil Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae)

Abstract

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Olivier) 1790, is currently the most harmful pest on date palm crop. Nowadays, the systematic and abusive use of synthetic pesticides to control insects that ravage crops is questioned following the awareness of the risks they generate for the environment and human health. Therefore, there is a need to search and develop alternative natural environmentally friendly strategies that can replace or reduce the use of chemical fertilizers and synthetic pesticides. In this context, a continuous and rigorous interest has been developed for the use of plant essential oils (EOs) and extracts that could constitute healthy alternatives to chemicals. This study aims to evaluate the insecticidal activity of essential oils obtained from four aromatic and/or medicinal plants, namely, Mentha suaveolens subsp. timija, Lavandula mairei, Artemisia mesatlantica, and Mentha pulegium, against larvae and adults of RPW, R. ferrugineus (Oliver) by contact. The four essential oils were tested at two different concentrations (0.5 μl/cm2 and 1.5 μl/cm2). A toxic effect was demonstrated for each essential oil tested. This effect depends on the concentration of the essential oil tested and the duration of exposure. For the toxicity of the EOs to larvae, EOs of Mentha pulegium developed the most important insecticide activity with very low LT50 (time required to kill 50% of the exposed insects) and LT90 (time required to kill 90% of the exposed insects) values of 9.45h and 22.16h respectively for 1.5 μl/cm2 concentration. Mentha suaveolens subsp. timija is in the second position with values of LT50 and LT90 of 19.35 h and 34.80 h respectively for a concentration of essential oil of 1.5 μl/cm2. The longest lethal times 50 and 90 are recorded with Lavandula mairei oils which required 52.44h and 107.25h to cause adult mortality of 50% and 90%, respectively. The essential oils of Artemisia mesatlantica recorded average values of LT50 and LT90 of 35.60h and 91.53h respectively. On the other hand, the shortest lethal times LT50 and LT90 for adult were recorded after 8.27h and 19.39h respectively of treatment with EOs of Mentha pulegium and Mentha suaveolens subsp. timija using the dose of 1.5 μl/cm2. The essential oil of Artemisia mesatlantica, classified as the second most toxic oil, showed average values of LT50 and LT90 of 22.68h and 30.09h, respectively for the concentration 1.5μl/cm2. Treatment with Lavandula mairei EO gives average values of LT50 and LT90 of 30.95h and 57.77h, respectively. Our study could be a basic guide for the possible field examination of the preventive (oviposition repellency) and curative action of the essential oils tested.