Toxicidade de extratos de timbós (Derris spp.) sobre Tetranychus desertorum (Acari: Tetranychidae) em folhas de pimentão

Abstract

The pepper is a vegetable of great importance socioeconomic in Brazil. Is among the ten most vegetables grown in country. Like most crops, many arthropods pests are associated with that culture, including some species of mites such as Tetranychus desertorum, reported infesting crops in Manaus. In most cases the mites are controlled by chemicals, which although effective can lead to problems both human health and the environment. In that sense, this work aimed to study the toxicity of extracts of Derris rariflora Benth. and Derris floribunda Benth. on T. desertorum leaf Pepper, aiming to offer products safer, cheaper and with less environmental impact. Plants were collected in natural areas, washed, dried and ground. Were then diluted in water distilled ethanol and acetone at concentrations of 0.5, 1, 10, 20 and 30%, resulting in aqueous extract, ethanol and acetone, these extracts were analyzed by High Performance Liquid Chromatography Efficiency. For bioassays, discs of pepper leaves were treated with extracts by dipping each disk and then received eight female mites. The commercial rotenone (98%) was also tested on the mites in concentrations of 0.1, 0.5 and 1%. It was found that rotenone is not present in aqueous extracts of the species. The extracts acetone and ethanol was found a rotenone content of 4.5 and 4% for D. floribunda and 4,3 e 5% for D. rariflora, not among them. The species D. rariflora was more toxic to the mite when compared to D. floribunda. Among the extracts, the ethanol was the most toxic followed by and aqueous acetone. The concentrations of 20 and 30% caused more mortality rates. The lowest LC50 was observed for the extract ethanolic D. rariflora. Rotenone commercial was not toxic to T. desertorum. However, except the aqueous extract of acetone and D. floribunda, which failed to achieve 50% mortality, the others were promising for control of T. desertorum on pepper leaves