Efeitos de extratos de Casearia javitensis Kunth (Salicaceae) sobre Sitophilus zeamais Motschulsky (Coleoptera, Curculionidae)

Abstract

Over millions of years of action of natural selection, certain plant characteristics were improved and resulted in plant species with different levels of susceptibility to attack by herbivorous insects. These characteristics are expressed in different ways, among these, plants can produce substances with insecticidal properties. There may be about two thousand plants which have their uses in the control of organisms harmful to agriculture. The use of plant extracts in storage environments aims to decrease in all stages of development of individuals in the population causing damage. The objective of this study was to evaluate insecticidal activity of organic and aqueous extracts of Casearia javitensis in different concentrations on Sitophilus zeamais in laboratory conditions. The extracts used in the bioassays were concentrated on rotaevaporator (organic extracts) and freeze dryer apparatus (aqueous extracts). In this work, we used six types of C. javitensis extracts that have been tested under two types of exposure, totaling 12 bioassays. The data were analyzed by means of multiple linear regression comparison test. The most promising extracts were aqueous extracts of leaves and branches, both in contact bioassays; and dichloromethanic extracts branches in intake bioassays. Among dichloromethanic extracts, concentration more effectively in control of S. zeamais is 10.4 mg / ml extract branches applied through ingestion of contaminated grains, registered mortality of 52%.