How monoterpene hydrocarbons could be an alternative insecticide for effective control of Lepidoptera defoliators?

Abstract

In Tunisia, Orgyia trigotephras (Lepidoptera, Erebidae) is considered among the most harmful pests for forests that cause significant damage to kermes oak and its maquis. Thus, the aim of this study was to evaluate the insecticidal effect of essential oils of Eucalyptus camaldulensis, E. kirtoniana, Thymus algerienis and T. capitatus toward the 3rd instar larvae of O. trigotephras. The chemical composition of essential oils was studied using GC-MS. Different concentrations of essential oils were used for contact action and compared to synthetic insecticide deltamethrin as a reference product. The insecticidal effects of the essential oils were evaluated by measuring the lethal time of 50% of larvae (LT50) and the lethal time of 100% of larvae (LT100). Eucalyptus essential oils were found effective when compared with the essential oil of Thymus spp. and deltamethrin. Their high toxicity may be attributed to their richness in monoterpenes hydrocarbons. Compounds belonging to monoterpenes hydrocarbons may constitute an alternative insecticide for controlling Lepidoptera defoliators outbreaks.