RELATIONSHIP BETWEEN INSECTICIDE-ACARICIDE RESISTANCE AND FIELD CONTROL IN TETRANYCHUS-URTICAE (ACARI, TETRANYCHIDAE) INFESTING ROSES

Field populations of the twospotted spider mite, Tetranychus urticae K och, were collected and tested to determine levels of resistance. Resi stance was detected. to fenbutatin-oxide (resistance factor [RF], 2.6- 464 at LC(95)), propargite (RE 3.9-135 at LC(95)), and fluvalinate (RF , 11-51 at LC(95)). Field populations of T. urticae were then sprayed with each acaricide and numbers of mites present monitored weekly to d etermine the efficacy of the spray. Field control failure of propargit e and fluvalinate was detected between RFs 88-135 and 23-51, respectiv ely, at the LC(95) level. There was no clear relationship between fenb utatin-oxide resistance and field control, Field control of T. urticae with fenbutatin-oxide appeared to be influenced by factors other than resistance.