TOXICIDADE DE EXTRATOS FOLIARES DE MARMELINHO-DO-CAMPO (Austroplenckia populnea) PARA A LAGARTA-DO-CARTUCHO-DO-MILHO (Spodoptera frugiperda)

Abstract

Resumo em língua estrangeira: Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), popularly known as the fall armyworm, is a polyphagous pest, but as its common name identifies, it is especially a problem for maize crop. In this work, the toxicity of different fractions of leaf extracts of Celastraceae Austroplenckia populnea (Reissek ex Mart.) Lundell was evaluated in a population of S. frugiperda under laboratory conditions. The crude extract of the leaves was obtained from the ethyl acetate. Refraction was carried out with solvents in increasing polarity: hexane, ethyl acetate and methanol. Through phytochemical prospecting, the following compounds of secondary metabolites in the leaves of this plant were identified: flavonoids, steroids, triterpenes, saponins and tannins. The extracts of A. populnea showed antifeeding effect for S. frugiperda moth, that is, some extracts were less attractive for caterpillars, however, the highest concentrations (5%) did not imply significant rejection of the leaf treated by the larvae. The lack of perception of insecticidal extracts during the act of feeding can be an interesting characteristic to be considered in the eventual use of these extracts as a pest control. An antibiosis effect was verified for the population of S. frugiperda when the larvaes were fed on short period of our study (24 h) with some of the fractionated extracts of this plant. Considering the antibiosis effect promoted by many of the treatments (crude extract and fractions) in a similar way to the control, our data suggest reduced toxicity of these extracts for S. frugiperda. There was no significant linear correlation between dose of extract and larval and pupal mortality. However, in general, lower concentrations (0.01 and 0.5%) of extracts resulted in higher mortality of larvae and pupae. Our experimental data suggest higher leaf consumption by caterpillars in the lowest concentrations of extracts, except for ethyl acetate extract. The extract that presented a lowest larval and pupal mortality for larvae and pupae was the hexanic. None of the extracts promoted prominent changes in the variable’s duration of larval, pupal, and adult phases, and in the insect's sex ratio. The notable antibiotic effect may be due to the small consumption of plant extracts, however, secondary metabolites isolated in synergism affected the biology of the studied pest.