Toxicidade de extratos de plantas medicinais obtidos com dióxido de carbono supercrítico à spodoptera frugiperda (J.E. Smith, 1797) (lepidoptera, noctuidae)

Abstract

The use of plants with insecticidal potential has been increasingly frequent. Control measures that cause less impact are of prime importance in controlling Spodoptera frugiperda, a lepidopteran known as fall armyworm and main pest of the agriculture of maize and rice, not only for the damage to crops, but also for the difficulty of its control, leading to a major loss in the productivity. Insecticide plants have stimulated a resurgence of the use of plant extracts for the control of these insects and are being utilized for possessing advantages when compared to chemicals, since they are easily biodegradable and can contribute to the production of botanical insecticides. Unlike the use of chemical synthetic and nonselective pesticides in agriculture, this work has as main objective to test the potential of active toxins in leaves of 9 medicinal plants (Aloe sp., Mikania sp., Casearia sylvestris, Syzygium cumini, Plectranthus neochilus, Jodina rombipholia, Piper umbellatum, Artemisia camphoratae Phyllanthus niruri). The extracts were obtained by conventional extraction using the following solvents: cold water, hot water decoction and 70% ethanol, all at room temperature, and supercritical fluid extraction with carbon dioxide at the temperature of 40°C and pressure of 100, 150 and 250 bar. The plant material was collected in São Leopoldo / RS Latitude: 29° 45 '39 "East; Longitude: 51° 08' 50" West within their vegetative cycles and the experiments were performed at the Laboratory of Microbiology and Toxicology at Unisinos. Bioassays were performed using second instar larvae placed on artificial diet of Poitout, with 15 subjects per treatment. One control was performed with water and the other with the solvent used. The results showed significant for Jodina rhombifolia, which showed 31% corrected mortality (CM) with ethanol 70% solvent. The results of supercritical extracts were significant for 250 bar, reaching 97% CM (LC 500.00472). The results of fractionated extracts suggest that J. rhombifolia efficiency for the control of S. frugiperda is related to the effect of synergism, thus being effective to control the target pest.