ESSENTIAL OIL FROM LEAVES OF Peumus boldus Molina COLLECTED IN AUTUMN TO CONTROL OF MAIZE WEEVIL Sitophilus zeamais Motschulsky

Abstract

Maize weevil (Sitophilus zeamais Motschulsky) is one of the major pests of stored grains world wide. Contact and fumigant toxicity, as well as repellent effects of essential oil from leaves of Peumus boldus Molina were tested in the laboratory against maize weevil. Leaves of Peumus boldus Molina were collected in autumn. The highest contact toxicity activity was obtained in concentrations of 2.0 and 4.0% (v/w) with 80 and 100% of mortality in the treated surface bioassay, and 81.1 and 100% in treated grain tests, respectively. In the bioassay of fumigant toxicity, the treatments of 30 and 35 µL essential oil 0.15 L-1 air showed 92.5 and 100% of dead insects. In the immature stage control bioassay, adult insect emergence (F1) in control was observed from week six, while treatments of 2.0 and 4.0% (v/w) of essential oil inhibited insect emergence in 100%. All the treatments assessed were repellents against adults of S. zeamais and maize germination was not affected when grains were mixed with essential oil. The essential oil of P. boldus has potential to be developed as a natural insecticide to control S. zeamais.