Abstract

Several plant species were selected as potentially safer substitutes for control of maize weevil, Sitophilus zeamais Motsch. The objective of the study was to investigate the insecticide irritability effect (that is, avoidance after contact) of ethanol extracts (0.05 gm.L^-1) of the species Croton heliotropiifolius (leaves and flowers), Duguetia furfuracea, Magonia pubescens, Senna obtusifolia, Senna occidentalis and Vernonia scabra, in comparison with a synthetic insecticide frequently used in treatment of grains, permethrin (Piredan EC (containing 384 gL^-1) DuPont do Brazil S.A., Barueri, SP, Brazil). Maize weevils of a single strain were subjected to free-choice tests with maize grains sprayed with the ethanol extracts and doses of permethrin. The behavioral response of S. zeamais to ethanol extracts and permethrin-sprayed surfaces differed from the control. As shown in the statistical analysis, the ethanol extract of flowers of C. heliotropiifolius induced significantly more contact avoidance behavior than all other plants tested. The results observed with the synthetic insecticide permethrin were similar to those obtained with C. heliotropiifolius, at a dose lower than recommended.

Key words: Maize weevil, toxicity, crude extract, velame, tingui.