Tuesday, 19 November 2002
D0263

This presentation is part of : Display Presentations, Section B. Physiology, Biochemistry, Toxicology, and Molecular Biology

Insecticide resistance and synergism in Brazilian populations of maize weevil

Berghem M. Ribeiro, Raul Narciso C. Guedes, Eugenio E. Oliveira, and Edmar S. Tuelher. Universidade Federal de Vicosa, Departamento de Biologia Animal, Campus Universitario, Vicosa, Minas Gerais, Brazil

Insecticide resistance to three organophosphate (chlorpyrifos-methyl, malathion and pirimiphos-methyl) and three pyrethroid (cypermethrin, deltamethrin and permethrin) insecticides was surveyed in nine field-collected populations of the maize weevil from six Brazilian States and contrasted with a standard susceptible population and a DDT and pyrethroid resistant population. Bioassay tests were carried out in glass-vials (20 ml) impregnated with dried insecticide residue and the resistant populations were recognised by using discriminating concentrations established from LC95s estimated for a standard susceptible population. Four field-collected populations had reduced susceptibility to cypermethrin (64-77% mortality) and to chlorpyrifos-methyl (76-77% mortality). All populations were susceptible to malathion and pirimiphos-methyl and only the DDT and pyrethroid resistant check showed resistance to all pyrethroids. Concentration-mortality curves showed non-significant levels of insecticide resistance in the field-collected populations and moderate (10- to100-fold) to very high levels (> 1000-fold) of resistance to pyrethroids in the DDT and pyrethroid resistant population. Results from insecticide bioassays with synergists (diethyl maleate, piperonyl butoxide, and triphenyl phosphate) suggested a major involvement of esterase as cypermethrin resistance mechanism, while no clear result was obtained for chlorpyrifos-methyl. Synergism results provide support for target site resistance to pyrethroids in the DDT and pyrethroid resistant population used in this study.

Species 1: Coleoptera Curculionidae Sitophilus zeamais (maize weevil)
Keywords: organophosphates, pyrethroids

Back to Display Presentations, Section B. Physiology, Biochemistry, Toxicology, and Molecular Biology
Back to Posters
Back to The 2002 ESA Annual Meeting and Exhibition