A field trial on apples in southeastern England showed that pre-bloom “pink bud” sprays of 4 synthetic pyrethroids—permethrin, cypermethrin, fenvalerate, and decamethrin, were all highly toxic to the predatory miteTyphlodromus pyri, but had no appreciable toxicity to the dominant spider mite species,Panonychus ulmi. The virtual elimination of the predatory mite at this growth stage of apples led to a marked population increase ofP. ulmilater in the same season. The use of these pyrethroids for insect control is incompatible with integrated mite management on apples usingT. pyri. Laboratory data supported the field results.