ACTION OF OURICURI PYROLIGNOUS EXTRACT ON THE Sitophilus zeamais Mot., 1855 (COLEOPTERA: CURCULIONIDAE)

Abstract

The corn weevil, Sitophilus zeamais Motschulsky, is an economically important primary pest that attacks maize grains. In warehouses, it is usually controlled by purging or fumigation. The advantage of using this fumigation is that it leaves no residues in the grains, but on the other hand the application periodicity is more frequent. The study of secondary compounds obtained from plants with fumigant and repellent properties has been widespread, aiming at the control of primary and secondary pests of stored grains. The objective of this work was to evaluate the toxic effect and repellent action of ouricuri (Syagrus coronata) endocarp pyroligneous extract to control corn weevil. At first, a contact and ingestion bioassay were performed with the following concentrations of the extract: 10, 30, 50 and 70µl, with five replicates each, plus the control. A Following, a fumigation test was also carried out with concentrations of 150, 200 and 250µl, with 5 repetitions each, plus the control. The evaluation of the tests was performed 48h after the experiment was set up with the quantification of the insect mortality rate. And finally, the repellency experiment was performed with the concentrations: 2.5; 10; 20; 40 and 70µl, with 5 repetitions (arenas) each. After 48h, the insects present in each container were quantified to calculate the repellency index (IR). In the contact and intake test, the applied extract affected the physical quality of the corn grains, making the experiment unfeasible. The fumigation test, even at the highest concentrations, did not show effective insect mortality, demonstrating the low fumigant action of the extract. On the other hand, the pyroligneous extract showed effective repellent action in all concentrations tested. Thus, it is concluded that the pyroligneous extract of ouricuri endocarp presents, at tested concentrtions, significant repellent action against S. zeamais.