Óleos essenciais de Croton grewioides e seus compostos majoritários : efeitos letais e subletais sobre o cupim Nasutitermes corniger (Blattodea : Isoptera)

Abstract

The termite Nasutitermes corniger (Termitidae) is an important pest in Neotropical regions, causing damage in agricultural, forest, and urban environments. The termite is managed mainly by means of synthetic organic insecticides. However, intense use of these products has had adverse effects, such as contamination of water and soil and harm to non-target organisms. In this scenario, plant essential oils (EOs) are seen as a more sustainable alternative to conventional insecticides. In this study, we evaluated the lethal and sublethal effects of the essential oil accessions of Croton grewioides (Euphorbiaceae) Cg112 and Cg126, and its major constituents (eugenol and methyl eugenol) on the termite N. corniger. Toxicity tests by topical application (LDs) and fumigation (LCs), survival tests, and individual and collective behavioral tests were carried out. Eugenol and EO from accession Cg126 were the most toxic compounds, requiring 0.67 and 1.94 g/mg by contact and 1.21 and 1.55 mg/L by fumigation, respectively, to cause 50% mortality of termites. In both exposure routes, all treatments reduced insect survival over time. Antennation, allogrooming, avoidance, aggregation, and butting behaviors were affected in relation to the control. All treatments caused repellency and affected termites walking movement, decreasing their speed and distance traveled. These results show that the essential oil of C. grewioides and its major compounds have promising potential and may be used in the synthesis of new insecticide molecules.