Insecticidal activity of extracts of Handroanthus impetiginosus (Purple Tabebuia) in Plutella xylostella (Lepidoptera: Plutellidae) larvae, as well as obtaining a new insecticide

Abstract

The objective of this research will evaluate the insecticidal activity of extracts obtained from bark, flowers and leaves of Handroanthus impetiginosus to diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) larvae. The extracts will be obtained from the bark, flowers and leaves using a process of cold maceration of the plant parts, spraying, filtration and rotary evaporator concentration under reduced pressure. In order to identify the most promising extracts for the control of P. xylostella, preliminary tests with ethanolic extracts of bark, flowers and leaves prepared from H. impetiginosus will be conducted. The treatments will be applied to leaf discs at a concentration of 2000 ppm (diagnostic concentration). As a negative control, deionized water and the solvent solution [acetone/methanol (1: 1, v/v)] will be used. Based on the results of screening the extracts, the most promising treatments will be evaluated again to estimate the LC50 and LC90 (the concentrations required to kill 50 and 90 percent of the larvae, respectively) and the EC50 (the concentration needed to reduce weight larval by 50%). The LT50 values (the time required to kill 50% of the population) for the most promising extract, will be estimated in concentrations that will be established according to the results obtained in this research. The efficacy of the most promising extracts in the greenhouse will be tested using a commercial insecticide based on flubendiamide as a positive control. The synthetic chemical insecticide will be used in the dose recommended by the manufacturer (416.7 ppm), while ethanol extracts of H. impetiginosus will be used in the values of LC90, which will be estimated in the previous tests. The intention is to obtain a new botanical insecticide that can be used in the management of P. xylostella.