Avaliação de óleos essenciais sobre Thaumastocoris peregrinus Carpintero & Dellapé, 2006 (Hemiptera, Thaumastocoridade)

Abstract

Eucalyptus is the greatest genus in the forest sector with a planted area of 5,473,176 hectares. This monoculture is suitable for the appearance of pest insects, especially Thaumastocoris peregrinus, popularly known as bronze - bug. The insect sucks the sap from the leaves, which look silvery, later evolving into a tan and making them to fall. Several control methods have been tested, including chemical control, biological control and alternative control with natural products and plant extracts. Thus, the objective of this work was to evaluate the essential oils of citronella (Cymbopogon winterianus Jowitt), patchouli (Pogostemon cablin (Blanco) Benth.) and lavender (Lavandula angustifolia Mill.) on the longevity of T. peregrinus adults. Four treatments were placed: sterilized distilled water (control); citronella essential oil; patchouli essential oil and lavender essential oil, all at 1% concentration. For the bioassays, Eucalyptus dunni leaves were immersed in the corresponding solutions and after evaporation of water excess they were provided to groups of 10 insects and kept in gerbox boxes sealed with plastic film and conditioned in a heated chamber (26 ± 2 ° C, 14 h photophase and 70 ± 10% RH). Fifty insects were used for each treatment, each insect was considered a repetition. The evaluations were performed every 12 hours, over a total period of 120 hours. Following the same methodology, patchouli oil was applied at different concentrations (1.25%, 1%, 0.75%, 0.5% and 0.25%). To identify the compounds present in the oils, gas chromatography of the oils was performed. After 108 hours of application, the treatment of patchouli essential oil caused total mortality of adult T. peregrinus individuals, differing significantly from the control with 95.7% of live insects and other treatments, citronella 22.9% and lavender 25.7%, of live insects. In the application of patchouli oil at different concentrations, it was observed that after 120 hours the survival of 0%, 10%, 20% 34% and 54% of the adult insects at the concentrations of 1.25%, 1% 0.75%, 0.5% and 0.25% of patchouli oil, respectively, and 68% for control. Chromatography of the essential oils identified a total of 16 constituents for citronella (C. winterianus), citronellal, geraniol and limonene being the major compounds with 34.15%, 10.45% and 7.98%, respectively. Patchouli chromatography (P.cablin) identified a total of 12 compounds, where the patchouli alcohol, α-guaienum and y-patchoulene were the major constituents with 21.99%, 18.32% and 16.44%, respectively, respectively. In the lavender oil (L. angustifolia) of a total of 12 compounds, three were major: 1.8 cineol (43.73%), trans-verbenol (12.77%) and fenchona (11.71%). The products tested reduced the longevity of adults of T. peregrinus, presenting potential for future studies and to be tested in control programs.