Potencial inseticida de óleos essenciais no manejo de Rhyzopertha dominica F. (Coleoptera: Bostrichidae) em milho armazenado

Abstract

The coleoptera Rhyzopertha dominica F. (Bostrichidae) is one of the main pests of stored products, causing qualitative and quantitative losses as reducing the nutritional and commercial value of the product. With the need to find alternatives to the use of chemical control, due to the development of insect resistance and the possibility of contamination of the products, the use of natural substances such as essential oils is proving itself as a promising alternative. Thus, this study aims to evaluate the insecticide activity of essential oils of basil (Ocimum basilicum), bitter orange (Citrus aurantium), Mint (Mentha spicata) and Velaminho (Croton pulegiodorus) on adult R. dominica in stored corn. Fumigation, contact and repellency tests were performed. The fumigation test was performed in containers made of glass with lids containing 10 individuals of R. dominica, in which the essential oils were applied in various concentrations (μL / L air) and after 48 hours of exposure to these oils the percentage of insect mortality was evaluated. For the contact test Petri dishes (6 cm Ø) were used with the essential oils diluted in 500 μL acetone and applied to filter paper of the same diameter, in different concentrations. After 24 hours the mortality of insects was evaluated. To evaluate the repellent effect two sublethal concentrations of each oil were used, estimated from previous tests, which are lower than the LC50. The tests were conducted in Petri dishes (Ø 6 cm) where filter paper discs were divided in half by applying one of the halves some of the oils concentrations (treatments), diluted in 500 μL acetone, and on the other only acetone (control). R. dominica individuals were released in the center of the plate and after 24 hours the metering was performed to count the insects found in each of the discs. In the fumigation test, in accordance with the LC50 and CL100, the toxicity of essential oils decreased in the following order: O. basilicum> M. spicata> C. pulegiodorus> C. aurantium. The essential oils of O. basilicum and M. spicata showed higher insecticidal effect on R. dominica, but the essential oils of C. aurantium and C. pulegiodorus promoted mortality in R. dominica only at higher concentrations. For the contact test, according to CL50, the toxicity of essential oils decreased in the following order: M. spicata> C. pulegiodorus> O. basilicum> C. aurantium. The essential oils of C. pulegiodorus and M. spicata showed higher toxicity by contact, while for the repellency test all essential oils were considered repellent. However, all the oils studied in this work showed insecticidal properties to promote the control of R. dominica and demonstrated potential use in the management of this coleoptera.