Genetic variability in Tetranychus urticae (Acari: Tetranychidae) from Greece: Insecticide resistance and isozymes

Resistance to methyl-parathion, methidathion, and methomyl was studied by bioassays in Tetranychus urticae Koch from Greece. At LC(50), the resistance ratio was highly variable with methidathion (5- to 63-fold) and with methomyl (6- to 34-fold). The mortality curves with methyl-parathion showed a clear plateau at approximate to 20% mortality, and the resistance ratio was approximate to 50 fold at LC(50) in all samples. By using isoelectric focusing on cellulose acetate membranes, electrophoretic studies of 5 loci encoding esterases (Est-1 and Est-2), glucose-phosphate isomerase (Gpi), malic enzyme (Me), and phosphoglucomutase (Pgm) disclosed large genetic differences among the samples.