Toxicity studies of synthetic pyrethroid insecticides to some predaceous phytoseiid mites: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours in the University of Canterbury

Abstract

The relative toxicity of two synthetic pyrethroid insecticides, cypermethrin and fenvalerate, to two strains of two-spotted spider mites, Tetranychus urticae Koch and three species of predaceous phytoseiid mites, Amblyseius fallacis Garman, Typhlodromus occidentalis Nesbitt and Typhlodromus pyri Scheuten was evaluated by the standard slide-dip and leaf spray techniques. Results from these laboratory bioassays indicate that both cyperrnethrin and fenvalerate were highly toxic to the three species of predator mites but these materials were relatively less toxic to T. urticae. At the recommended field application rate of 0.005% a.i., cypermethrin and fenvalerate cause significantly high mortality of the three predator species. The pest spider mites were not significantly affected at this rate.