Bioatividade do óleo essencial de Pogostemon cablin Benth (Lamiaceae) para Callosobruchus maculatus (Coleoptera: Chrysomelidae)

Abstract

The bean weevil Callosobruchus maculatus (Fabr.) (Coleoptera: Chrysomelidae) is an important pest of stored grains, which prefers legumes. In this sense, biopesticides have been considered a possibility for the control of this insect, mainly to delay the selection of resistant insect populations. Thus, the objective of this study was to determine the toxicity of Pogostemon cablin essential oil (EO) for C. maculatus. The insects used in the bioassay were obtained from rearing kept under laboratory conditions. Adults aged between 1 and 6 days, from rearing kept on chickpeas, were used. Pots (120 mL) with perforated plastic lids to allow gas exchange were used to conduct the assay. Chickpeas (20 g) and adults of C. maculatus, 5 males and 5 females, were added to each experimental plot. The treatments used were P. cablin EO at concentrations of 0; 0.5; 0.90; 1.6; 2.8 and 5 µL of EO/20 g of chickpeas. Insect survival was evaluated every 24 h for 120 h. For concentrations of 2.8 and 5 µL of EO/20 g of chickpeas, the median lethal time (LT50), i.e., the time required to cause 50% mortality in the population, was 24 h. For the other treatments, the LT50 was greater than 120 h. The probability of survival at the end of the experimental evaluation period was 15.6 and 3.0%, respectively, for concentrations of 2.8 and 5 µL of EO/20 g of chickpea, differing statistically from the other treatments. Thus, the toxicity of P. cablin EO for C. maculatus can be confirmed. Further studies will be conducted with the aim of exploring the potential of P. cablin EO for the control of C. maculatus