Ecologia química de Thyrinteina arnobia STOLL, 1782 lepidoptera geometridae em eucalipto

Abstract

The genus Eucalyptus has about 600 species, adapted to the most varied climates and soils. In Brazil, around 7.47 million hectares are occupied by eucalyptus forest stands. With the advance of eucalyptus cultivation in Brazil, the incidence of population outbreaks of insects has been favored. Among the insect pests of the crop, the defoliator caterpillar Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) stands out, cited as the most important lepidopteran for eucalyptus cultivation in the country. In the state of Alagoas, the presence of T. arnobia was found to cause significant damage. Due to the large extension of the eucalyptus forest stands and the height of the trees, the chemical control of T. arnobia becomes economically unsustainable. As a result, new control methods have been proposed, including behavioral control, through the study of the sexual pheromone of T. arnobia. Therefore, it is necessary to understand the mechanisms involved in the chemical ecology of the species, from the sexual pheromone release process, through the perception of these compounds, excitation and response to pheromonal substances. Thus, the present study aims to study the chemical ecology of T. arnobia and as specific objectives: (i) provide basic and complementary information on the sexual behavior of T. arnobia, based on the observation of the calling behavior; (ii) carry out the study of antennal sensilla in males and females of T. arnobia, through scanning electron microscopy (SEM); (iii) isolate and identify possible pheromonal substances from extracts of abdominal glands of T. arnobia females, using gas chromatography with flame ionization detector (GC-FID); (iv) and verify the bioactivity of the extracts, through electroantenography coupled to gas chromatography (EAG-GC). Regarding calling behavior, gland exposure occurred after the 2nd hour of scotophase. The calling behavior was characterized by the exposure of the pheromone gland of the females of T. arnobia, the dissemination of the sexual pheromone, the perception of the pheromone by the males and the approach of the males to the emitting source of the pheromone. In total, six types of sensilla were identified in antennae of females and males of T. arnobia, characterized in trichoid, squamiform, caetic, basiconic, celoconic and styloconic. The antennae of female and male T. arnobia have different structural morphology of sensilla. Antennae of both sexes have Böhm's bristles at the base of the scape. The trichoid sensilla are the most abundant, mainly in the antennae of T. arnobia males, indicating that they can respond to stimuli from chemical substances. In the chromatographic profile of the extract of abdominal glands in T. arnobia females from Alagoas, it was possible to previously identify 19 possible compounds. Regarding the bioactivity of pheromonal substances from extracts of abdominal glands of T. arnobia females, it was observed that the electroantennary responses of male antennae submitted to the pheromonal extract of T. arnobia were significant when compared to the hexane stimulus (control). Keywords: defoliator caterpillar; semiochemicals; calling behavior; sensilla; pheromonal gland; bioactivity.