Efeitos do extrato de folhas e flores de Tithonia diversifolia (Hemsl.) A.Gray (Asteraceae) sobre pragas de armazenamento

Abstract

Recently, the spread of pests/insects that attack grains has grown significantly, due to the resistance acquired by successive applications of chemical insecticides, causing physical and economic damage. Thus, it is necessary to use an effective biopesticide to control insects. Therefore, the objective of this study was to evaluate the chemical composition and the insecticidal potential of the alcoholic extract of leaves and flowers of Tithonia diversifolia on the control of the pests Acanthoscelides obtectus and Sitophilus spp. The plant material (leaves and flowers) was collected at EMATER- GO, the plant was also collected for the manufacture of an exsiccate, which was sent for identification and deposit in the Herbarium of the Universidade Estadual de Goiás do Campus Central - Sede Anápolis (registration no. UEG-14411). The Tithonia diversifolia extract was prepared using the method of direct extraction in solvents, with the aid of ultrasound for 40 minutes and then the solvent was evaporated under reduced pressure with the aid of a vacuum rotary evaporator, the process being carried out until obtaining 1286 ml .To identify the main classes of secondary metabolites present in the material, a phytochemical screening was performed, resulting in the detection of alkaloids, tannins, flavonoids, coumarins, terpenes and saponins. The plant material extract of Tithonia diversifolia was evaluated for its chemical composition by High Performance Liquid Chromatography (HPLC). A bioassay was performed to evaluate insect mortality at six concentrations (0; 10; 100; 350; 700 and 1000 mL L - 1) ; (0; 300; 650; 1000; 1350, and 1700 mL L -1) of fatty extracts and supernatant respectively. To test plant extracts for insect control, each experimental unit consisted of 10 non-sexed adult individuals. Every 24 hours of control, the number of dead insects was counted. The experimental design was completely randomized, in a 6 x 7 factorial scheme, for the two insects, being the factors concentrations and evaluation periods, with three replications. The results obtained allowed us to conclude that, the Fatty Extract at a concentration of 1000 mg L-1, had a mortality of 90% of Acanthoscelides obtectus insects, Supernatant Extract at a concentration of 1000 mg L-1, presented a mortality of 70% of Acanthoscelides insects obtained. Fatty Extract at a concentration of 1700 mg L-1, showed a mortality of 50% of Sitophilus spp insects xiii and, at a concentration of 1700 mg L-1, it presented a mortality of 40% of Sitophilus spp.