Insecticidal and repellent effects of essential oil Eugenia uniflora L. (Myrtaceae) on Sitophilus zeamais Mots. (Coleoptera: Curculionidae)

The objective of this work was to evaluate the insecticidal and repellent effects of Eugenia uniflora (Myrtaceae) essential oil (EUEO) on Sitophilus zeamais (Coleoptera: Curculionidae) and to identify the chemical compounds of this oil. Three experiments were carried out to evaluate the insecticidal effect (immersion of the insect, volatilization and spraying on corn grains) and one for the repellent effect. Different concentrations of EUEO (0; 0.31; 0.62; 1.25; 2.5; 5; 10%) were prepared. Seven plates (replicates) were prepared per treatment, containing 15 adult insects each. For the immersion of the insect and spraying experiment on corn grain, the evaluations were performed at intervals of 1; 6; 12; 24; 48; 72; 96 h. For the volatilization experiment, the evaluation was done at intervals of 12; 24; 48; 72 and 96 h, quantifying the dead insects. In the repellency experiment, the E. uniflora oil was evaluated at 2.5% in an arena consisting of five polyethylene containers. The evaluation was performed after 24 h, quantifying the number of insects in each container. In order to identify the chemical compounds of the EUEO, gas chromatography analysis was performed by mass spectrometer. In the immersion experiment, mortality was found at 10% concentration, differing significantly from the control. In the volatilization experiment, there was no significant mortality within and between the application times in any of the treatments. In the spraying experiment on corn grains, it was found that the concentrations 2.5%, 5% and 10% caused the highest mortality rates, respectively, of 85.71%, 100% and 100%, differing from the control. The 2.5% EUEO has a repellent effect for S. zeamais adults. Regarding the identification of the essential oil compounds, the major compounds identified were sesquiterpenes of Calamen-10-one and Silfiperferol-6-in-5-one. The EUEO spraying on corn grain has acute insecticidal and repellent effect on S. zeamais, and containing sesquiterpenes as major constituents.