Bioatividade de óleos essenciais de lamiáceas para Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae)

Abstract

The fall armyworm Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is a polyphagous pest that causes damage to several economically important crops. The main methods of controlling this pest are genetically modified plants that express the Bt protein and chemical insecticides, that are not sustainable methods; however, the selection of resistant populations is reported.Thus, in this work, three bioassays were conducted with the objective of evaluating the bioactivity of essential oils (EOs) of plant species of the Lamiaceae family: Lanvandula angustifolia Mill., Pogostemon cablin Benth., Salvia sclarea L.and Thymus vulgaris L.against S. frugiperda. For all bioassays, diets with added water orTween 80 1% aqueous solution were used as control. In the first trial, the EOs were added to an artificial diet and offered to S. frugiperda caterpillars in an ingestion trial, with no choice. It was found that caterpillars fed the artificial diet containing the EO of P. cablin had a survival probability of 0.18, that is, mortality rate of 82%. In the second bioassay, different concentrations of P. cablinEO were added to the artificial diet in order to determine the time-concentration-mortality relationship. The median lethal concentration (LC50) was estimated in 0,9270 ± 0,02858 mg of EO/mL of diet. While the LC90 was 1,5632± 0,08160 mg of EO/mL of diet. In addition, a reduction in the weight of caterpillars that were fed with the EO of P. cablinwas observed. A third trial was carried out with the objective of evaluating the food preference and consumption of S. frugiperda caterpillars, when they were offered, with a free choice, a diet containing the negative controls and P. cablin. There was no difference in the number of caterpillars that opted for the diet with the control, aqueous solution of Tween 80 at 1%, and the treatment containing the EO of P. cablin; however, there was a reduction in food consumption, the average consumption in the control aqueous solution of Tween 80 1% was 177.65 ± 9.6602, whereas for P. cablin EO the consumption was 122.22 ± 8 .1486 mg. Thus, it can be seen in this work that the EO of P. cablinhas substances that are capable of causing mortality, reduction in weight and food consumption of S. frugiperda caterpillars