CONTROLE DE Spodoptera frugiperda (LEPIDOPTERA:NOCTUIDAE) (J.E.SMITH,1917) COM O EXTRATO ETANÓLICO DE Asclepias curassavica L.

Abstract

The A. curassavica plant is characterized as a toxic plant for vertebrates, and little is known about its effect on invertebrates, such as insects. Thus, a study was conducted to verify the action of A. curassavica on S. frugiperda. The plants were collected, dried and ground, and the raw ethanolic extract was made from the powder. This was added to the diet offered to caterpillars in two trials, one at concentrations of 1%, 2% and 4%; and another at concentrations of 0.05%, 0.1% and 0.5%. The parameters evaluated were: mortality; food consumption; weight of larvae and pupae; fertility (number of eggs and% of hatching). Two trials (one with second instar caterpillars and one with fifth instar caterpillars) of topical applications of the extract at concentrations of 1%, 2%, 4% and 6% were conducted to verify contact action through mortality after treatment. The experiments were performed with and without a choice, using corn leaf disks immersed in ethanolic extract at concentrations of 1%, 2% and 4%, where food intake (g) and preference index were evaluated. A trial was conducted evaluating total polyphenols and flavonoids in extract A. curassavica in order to verify the presence and measure them. The extract of A. curassavica added to the artificial diet, caused mortality of S. frugiperda in all concentrations, with 1%, 2% and 4% showing 100% mortality, and also 0.5% with 98% mortality. The prolongation of the larval period was evidenced in the treatments 0.1% and 0.5%, in 1.29 and 10.75 days respectively, in relation to the control. There was a reduction of larval weight in treatments 0.05%, 0.5%, 1%, 2% and 4% in 15%, 77%, 17%, 97% and 100%, respectively. On the pupal weight, the weight of the pupae in the treatments was 0.05%, 0.1% and 0.5% in 10%, 22% and 54% respectively; already in the weight of the female pupae, there was reduction with the treatment 0.1% in 9.5%. Food consumption was reduced in treatments 0.5%, 1%, 2% and 4% in 22%, 40%, 47% and 57%, respectively. The excreted faeces weight in the treatments 0.1%, 1%, 2% and 4% was 0.730g, 0.002g, 0g and 0g, respectively. At no concentration interference was observed in the number of postures, number of eggs and percentage of hatching. On topical application in the second instar caterpillars, contact action was verified in all concentrations, standing out the 6% treatment that caused 100% mortality after 72 hours of application. However, in the trial with fifth instar caterpillars, there was no contact action in the treatments used. In the tests with and without chance of choice, there was difference in food consumption in all concentrations, especially the reduction in treatment 4%. All treatments were classified as phagdeterrents, and the 4% treatment was less preferred. It was verified the presence of total polyphenois and flavonoids in the extract, presenting 58.75 ug / ml and 150.1 ug / ml, respectively. The extract of A. curassavica should be tested in the field at the concentration of 0.5%, because in this concentration causes high mortality (98%) with the lowest amount of input.