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

Field populations of the twospotted spider mite, Tetranychus urticae Koch, were collected and tested to determine levels of resistance. Resistance 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 determine the efficacy of the spray. Field control failure of propargite and fluvalinate was detected between RFs 88-135 and 23-51, respectively, at the LC(95) level. There was no clear relationship between fenbutatin-oxide resistance and field control, Field control of T. urticae with fenbutatin-oxide appeared to be influenced by factors other than resistance.