Avaliação da atividade inseticida dos extratos de Annona mucosa (Jacq.) (Annonaceae) sobre Sitophilus zeamais Motschulsky (Coleoptera, Curculionidae)

Abstract

In recent decades the use of synthetic insecticides has increased in the control of insect pests, but the use of these products generates numerous negative impacts such as contamination of soil, water, manipulator and food itself. Faced with this problem, we have sought new forms of control, more specific and less impact on the environment. New alternative measures are being tested with the use of plants. The objective of this study was to evaluate the insecticidal action of the extract and fractions of Annona mucosa seeds in the control of Sitophilus zeamais Mots. (Coleoptera: Curculionidade). The extract was obtained by maceration in ethanol, and the fractions were obtained in organic solvents by liquid-liquid partition (hexane and ethyl acetate) in increasing order of polarity. In order to verify the bioactivity of the extract and the fractions, in this sense the fractions in hexane of A. mucosa were the ones with the highest insecticidal effect for the control of S. zeamais, in comparison to the other treatments. The hexanic fractions had better mortality results through ingestion (100%), when compared to contaminated surface contact (50%). The median lethal concentration (LC50 = 2,824 and 4,738 ppm) presented higher mortality for the ingestion and contact test. Considering the results obtained, in the conditions of the present study, it was possible to conclude that the fractions in hexane of A. mucosa from the ethanol extract obtained by liquid-liquid partition are promising grain protectors against S. zeamais, providing satisfactory levels of control. However, it is fundamental to analyze the phytochemistry of the fractions, determining the most active active principle in insect mortality, as well as to evaluate the toxicity of the fractions in order to make the results of this study into a commercially viable product.