SEASONAL VARIATION OF REPELLENCY OF ESSENTIAL OILS OF MONIMIACEAE AGAINST Sitophilus zeamais Motschulsky (CURCULIONIDAE)

Abstract

Sitophilus zeamais (maize weevil) in stored cereals is mainly controlled with the use of synthetic insecticides. Botanical insecticides, particularly essential oils, are an alternative to use of synthetic insecticides. In Chile, the best results have been obtained with the use of essential oils of Peumus boldus (boldo), Laurelia sempervirens (laurel) and Laureliopsis philippiana (tepa). A study was conducted in the laboratory to evaluate the repellency of these three extracts against S. zeamais throughout the year. The main components of each essential oil were: 1-8-cineol (from 14.9 to 40%) and ascaridol (24.37%) in P. boldus; methyl eugenol (from 4.6 to 39.7%) and safrole (from 38.5 to 64.7%) in L. sempervirens; safrol (from 17 to 39.6%) and linalool (from 0. 9 to 34.5%) in L. philippiana. Except for the extracts of L. philippiana and P. boldus at 0.125 and 0.25%, all treatments caused repellency, reaching higher levels at concentrations > 4%. Only the essential oil of L. sempervirens presented seasonal variation, with greater repellency in the foliage collected in summer. Due to the absence of seasonal effects, essential oils of P. boldus and L. philippiana are considered promising for the control of pests in stored grains throughout the year.