Artificial laboratory selections for resistance and susceptibility to fenpyroximate were performed in a population of Tetranychus urticae Koch, collected from a commercial strawberry field in the State of São Paulo, Brazil. After five selections for resistance and three selections for susceptibility, the resistance ratio (R/S) at the LC50 reached 2,912. Cross-resistance relationships between fenpyroximate and other eight acaricides were evaluated using the selected susceptible and resistant strains of T. urticae. The results indicate positive cross-resistance between fenpyroximate and the acaricides pyridaben and dimethoate; and negative cross-resistance between fenpyroximate and milbemectin. No cross-resistance was detected for the acaricides abamectin, fenpropathrin and cyhexatin. The genetics of fenpyroximate resistance was also studied. The inheritance of resistance was consistent with the hypothesis of control by one major, incompletely dominant gene. No extra nuclear effects were found.
Species 1: Acari Tetranychidae Tetranychus urticae (twospotted spider mite)
Keywords: Resistance Management, Acaricide
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