Insecticidal Effect of Extracts from Native Plants to Mato Grosso do Sul, Brazil, on Sitophilus zeamais Mots. (Coleoptera: Curculionidae)

Abstract

Research on insecticidal plants has increased in recent years, as has their utilization. Their compatibility with other methods of insect control and their lower toxicity to mammals are some of the advantages that have fostered their use. In the present study, selected plant species native to the state of Mato Grosso do Sul, Brazil, were investigated for their insecticidal potential against Sitophilus zeamais Mots. The extracts assayed were obtained from stems of Tapirira guianensis Aubl. (Anacardiaceae), Schinus terebinthifolius Raddi (Anacardiaceae), Tabebuia heptaphylla (Vell.) Toledo (Bignoniaceae), and Gomphrena elegans Mart. (Amaranthaceae). Wheat grains were treated with the extracts and distributed into acrylic containers, each holding 20 unsexed 10- to 20-day-old S. zeamais adults. For the control the wheat grains were treated solely with solvents. The number of dead insects was counted daily until the tenth day. T. heptaphylla and G. elegans extracts exhibited insecticidal effect since the fifth day of treatment, whereas the effect of the other extracts was not observed before the tenth day. Insect death was caused by the following extracts: T. guianensis in n-butanol, hexane, and dichloromethane; S. terebinthifolius in ethanol, ethyl acetate, hexane, and dichloromethane; T. heptaphylla in acetonitrile-chloroform, ethanol, and hexane; and G. elegans in ethanol, hexane, dichloromethane, ethyl acetate, and as hydroalcoholic extract. G. elegans extracts had the strongest insecticidal effect of all the species tested.