Toxicidade da fração hexânica de frutos e sementes de Ricinus communis para lagartas do complexo Spodoptera

Abstract

The use of plant extracts has become increasingly frequent as a pest management strategy, mainly due to the diversity of chemical compounds present in plants with insecticidal potential, low toxicity to mammals, in addition to being more sustainable. In this bias, castor bean, Ricinus communis L. (Euphorbiaceae) is a plant that stands out as a potential tool, as it has insecticidal potential and is easily found throughout the national territory. In this sense, the present work aimed to evaluate the effect of the hexane fraction of the crude extract of fruits and seeds of R. communis (FHFSRC) on eggs of S. cosmioides and S. frugiperda and on caterpillars of different instars of S. cosmioides, S. eridania and S. frugiperda, under laboratory conditions, in two application modalities (contact and ingestion), in addition to identifying the compounds present in the hexane fraction of the crude extract by means of high performance chromatography (HPLC-ESI-Q- TOF-MS/MS). To this end, three bioassays were carried out: 1) Effect of 2% FHFSRC on eggs of S. cosmioides and S. frugiperda; 2) Lethal effect of 2% HFSFRC, applied topically on first, second, third and fourth instar caterpillars of S. cosmioides, S. eridania and S. frugiperda; 3) Lethal effect of 2% FHFSRC applied to soybean leaf discs and arranged for first, second, third and fourth instar larvae of S. cosmioides, S. eridania and S. frugiperda. It was verified that the 2% FHFSRC had a toxic effect for eggs of S. frugiperda and S. cosmioides, totally reducing the hatching of the larvae, and for the four instars of the three species of insects evaluated, as much as applied topically, when applied on the food. As for the chromatography performed by the FHFSRC, five compounds were identified in the hexane fraction, being three flavonoids, one ricinoleic acid and cinnamic acid. The FHFSRC at 2% has an ovicidal and acute insecticidal effect on the caterpillars of the studied species, configuring itself as a potential insecticide to be used.