Formamidine synergism of pyrethroid toxicity to twospotted spider mites (Acari:Tetranychidae) [Tetranychus urticae]

The toxicity of binary mixtures of formamidines and pyrethroids to Tetranychus urticae was investigated and compared with the toxicity of their individual components. A synergistic interaction was observed with 85 of the 104 formamidines examined in binary mixtures with cypermethrin; 29 of these improved toxicity 5-fold or greater. With regard to the different pyrethroids, there was evidence for suggesting that formamidine with fluvalinate, flucythrinate, and fenpropathrin, and least with fenvalerate and permethrin.