Potencial inseticida de extratos orgânicos de algodão-de-seda à Spodoptera frugiperda

Abstract

Spodoptera frugiperda is considered a difficult-to-control insect-plague. For this reason, research has been carried out to evaluate new methods of alternative controls, such as the use of insecticidal plants. In this context, the use of aqueous extract of silk cotton, Calotropis procera, has shown promise for the control of harmful insects and microorganisms. The objective of this study was to evaluate the insecticidal effect of the raw methanolic extract of silk cotton leaves and their fractions on the survival and development of S. frugiperda. Bioassays were performed with the crude methanolic extract and hexane, ethyl acetate and methanolic fractions both applied on corn leaves and placed on an artificial insect diet. In the corn leaf experiment, these fragments were immersed at each of the concentrations evaluated and transferred to glass tubes where a five-day old caterpillar was also placed. For the bioassay with artificial diet, disks of this were treated with 0.1 mL of each of the evaluated concentrations. The discs were placed in glass tubes along with a five-day old S. frugiperda caterpillar. The estimated lethal concentrations, LC50 and LC90, for crude methanolic extract to S. frugiperda caterpillars applied to corn leaf were 0.54 and 2.08%, respectively. The estimated lethal concentrations, LC50 and LC90, the crude methanolic extract to S. frugiperda caterpillars applied to the artificial diet were 2.01 and 4.76%, respectively. The crude methanolic extract at the concentration 2.14% caused the highest percentage of death of caterpillars and deformed pupae. The oviposition period, total number of postures and total number of eggs were significantly affected by the ingestion of the extract and its fractions. The methanolic fraction caused the highest percentage of deformed adults, and the main defect observed was the malformation of the wings. The crude methanolic extract also caused the elongation of the larval and pupal phases of S. frugiperda. It is concluded that the crude methanolic extract of C. procera and its hexane, ethyl acetate and methanolic fractions affect the survival and development of S. frugiperda.