Toxicity of Machaerium opacum (Fabaceae) Leaf Extracts Against Fall Armyworm (Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Abstract

Secondary plant metabolites have been widely studied as pest control agents. In this paper we report secondary compounds present in Machaerium opacum leaves, as well as the toxicity of different fractions of the extract of this plant to fall armyworm (Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)) under laboratory conditions. Crude extracts were obtained by means of ethanol. Refractionation was carried out with the solvents hexane, dichloromethane, methanol and ethyl acetate. By means of preliminary phytochemical prospection, starting with the ethanolic extract, flavonoid, triterpene, anthraquinone, coumarin, tannin and steroid compounds were identified. In the ethanolic fractions, triterpene compounds were identified in a mixture (α-amyrin and β-amyrin), as well as lupeol and the acyclic diterpene alcohol, phytol. In methanolic fractions, the flavonoid rutin was found. In the dichloromethane fraction, the flavonoid mucronulatol and its isomer, isomucronulatol, were found. Extracts of M. opacum did not present an antifeedant effect on the larvae of S. frugiperda. However, all fractions of the extracts tested promoted significant antibiosis effects (reduced weight in the larvae and pupa, larval and pupal mortality and prolongation of the adult phase) on the test population of S. frugiperda. Therefore, our results showed the insecticidal potential of leaf extracts of M. opacum against S. frugiperda.