Toxicidade e formulação de extratos de Annona muricata L. (Annonaceae) para o controle de Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae)

Abstract

The diamondback moth, Plutellaxylostella (L., 1758) (Lepidoptera: Plutellidae), is the major pest of crucifers worldwide, mainly because of its ease of dispersion, short cycle and high capacity to develop resistance to insecticides. Therefore, the adoption of alternative control methods is important for the development of an integrated management plan for the species. Among these methods, there is the use of plant extracts with insecticidal activity such as species of the family Anonnaceae like soursopAnnonamuricata L. (Annonaceae) has reportedinsecticide,acaricideand vermicideactivity. Thus , this study aimed to evaluate the effect of different solvent extractors of soursop seed in mortality , biology and oviposition of P. xylostella and its residual efect in plants, and subsequently to extract the best feasible to develop a formulation for the control of pests. Experiments were performed to determine the lethal and sublethal concentrations of three extracts (aqueous, hexane and ethanol) to determine the LC50 and evaluations of the effect of the extracts on insect biology and oviposition, as well as the residual effect of the extract. With the most promising extract was prepared microencapsulated formulation using "Spray drying" technique. The analysis of extracts showed that the LC50 and LC99 were 0.013 and 0.084 %, 0.025 % and 0.196, 2.33 and 35.22 % for the ethanol extract, hexane and aqueous, respectively. The organic extracts affected the development of the pest, and lower larval viability, but did not affect pupal stage. Furthermore, the ethanol extract on lethal concentration proved effective as oviposition deterrent, and negatively affected the embryonic stage. In relation to the residual effect, the ethanol extracts lethal and sublethal concentrations differed from the control until the 4th Day after application, thus showing that the extract may persist on the plant for at least this period. Could not find a stable emulsion for organic seed extracts of A. muricata. The ethanol extract microencapsulated showed results similar to those of the ethanol extract , with a sublethal concentration of 0.025% a lethal concentration of 0.3% , affected the development of the pest and persistence in the plant was at least four days. The microencapsulated formulation is promising to be used by farmers, but still needs tweaking for application.