ABSTRACT
The acaricide resistance in Tetranychus urticae Koch has been registered in several countries including Brazil. The objective of this study was to detect the resistance of T. urticae to the acaricides abamectin and fenpyroximate, and to evaluate the resistance frequency in commercial fields of several crops in the state of São Paulo. Discriminating concentrations of 4.79 mg of active ingredient (A.I.)/L for abamectin and of 46.3 mg of A.I./L for fenpyroximate were established for monitoring T. urticae resistance to these acaricides. Twenty nine mite populations were collected from commercial fields of different crops (strawberry, bean, fig, raspberry, papaya, peach, tomato, chrysanthemum, aster, goldenrod), in 15 counties in the state of São Paulo. Bean-leaf-disc arenas were infested with T. urticae mites and submitted to acaricide spraying at the discriminating concentration of each chemical, using a Potter spray tower. The percentages of survival were registered 48 hours after treatment. The results showed significant differences among populations in their responses to abamectin and fenpyroximate. Populations with frequencies of resistance from zero to 81.3% were observed for abamectin, and from zero to 94.5% for fenpyroximate. The highest frequencies of resistance were registered from populations collected at ornamental plants.
KEY WORDS
Two-spotted spider mite; acaricide resistance; strawberry; chrysanthemum