Emulsões e estudo das frações químicas do extrato de Annona muricata L. (Annonaceae) para o controle de Plutella xylostella (L.,1758) (Lepidoptera: Plutellidae)

Abstract

The Brazil is a country that leads the use and marketing of pesticides due to indiscriminate use in crops, leading to resistance mechanisms and contamination of the environment and consumers. Every day, has been growing studies with the use of alternative pest control methods, including the use of insecticides, plants that cause a minor effect on the environment.The Diamondback moth, Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae), is the main large plague worldwide, mainly due to its easy dispersion, short cycle and great ability to develop resistance to insecticides. For this reason, the adoption of alternative control methods is important for the development of an integrated management plan for the species. One of these methods, the use of plant extracts with insecticidal action such as species of the family Anonnaceae, such as graviola Annona muricata L. (Annonaceae) that has reports of activity insecticide, acaricide and vermicida. With this, the aim of this study was to obtain a formulation based on stable emulsion of ethanolic extract of seeds of graviola, assess the organoleptic characteristics, analyze the stability of the systems formed in the long and short term and assess their activity on the moth-cruciferous plants. Also, the chemical fractionation of the ethanolic extract of graviola monitored by Kedde reagent for the screening for the presence of acetogeninas and to test its effects on biological control of P. xylostella. Of the five ways of obtaining the emulsion, the emulsion only 5 showed stable and homogeneous achieved by the amount of 3.5 g, 2 g Tween Span, 10 g of the extract orgânio and 85 g of H2O. The results showed that emulsions stored without direct sun, were stable for three months and the emulsions that were subjected to short-term stability tests it has been observed that when exposed to high temperatures were unstable in the observed period. The estimate of the LC50 and LC99 were 0.03 and 4.26%. The emulsion affected the development of prague and decreased the viability of caterpillars whose results found for witness, to the chemical control and LC50 were 98.3; and 70.0; 70.0% respectively. However, proved effective as oviposition repellent and also negatively affected the embryonic stage whose results found for witness, to the chemical control, to LC50 and LC99 were 96.5; 79.50; 87.0; and 21.50%, respectively. With the completion of chemical fractionation was obtained four fractions by means of a partition – liquid – liquid that were: chloroform, Methyl acetate, hexanica and biological tests were carried out and water with traces of cruciferous and the data obtained were tracked mortality of p. xylostella was affected after the implementation of all fractions of the ethanolic extract. However the chloroform fraction was presented a 67.74% LC50 mortality and to apply the LC99 a mortality rate of 98.3%. Then a filtering funnel with silica and obtained six fractions that were methanol, ethyl acetate, hexane, 10% + 90% acetate, hexane, 25% + 75% acetate 50% acetate, hexane and + 50% hexane and mortality of caterpillars of P. xylostella was elevated in all fractions passed by hopper with silica purification, but the fraction 25% + 75% acetate, Hexane was presented the greater mortality featuring 64.76% on LC10. In all the most active fractions were confirmed the presence of the violet coloration acetogeninas presented in thin layer chromatography (CCD).