Caracterização química e atividade inseticida do óleo essencial de Thymus vulgaris L. (Lamiaceae) sobre Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae)

Abstract

The greenhouse whitefly (Trialeurodes vaporariorum) is one of the most important agricultural pests in the world. Its control is based on chemical insecticides, wich are known for causing damage to the environment. The objective of this study was to evaluate the chemical composition and bioactivity of thyme essential oil (Thymus vulgaris) on whitefly eggs, nymphs and adults. Aliquots of essential oil (0,1; 0,5; 1,0; 1,5; 2,0% v/v) diluted in Tween®-80 0,5% v/v, were sprayed on tomato leaflets infested with the insect at its different biological cycle stages. For eggs and nymphs bioassays, five replications were performed for each treatment. For the adult bioassays, five repetitions were performed per treatment, with 5 individuals per repetition. Two negative controls were used: with distilled water and with Tween®-80 (0,5% v/v), and two positive controls, with the chemical insecticides Chess® (40 g/100 L) and Oberon® (500 mL/ha). . The major compounds found in thyme oil, by GC-MS and GC-FID, were ?-cymene (32,28% w/w), followed by thymol (25,99% w/w) and ?-terpinene (12,55% w/w). The higher mortality rates observed were in the tests with whitefly nymphs, were the medium mortality ranges from 76 to 96%, from the concentration 0,5% v/v.(sic)