Chlorfenapyr resistance in two-spotted spider mite (Acari: Tetranychidae) from Australian cotton.

The responses of Tetranychus urticae Koch from Australian cotton to chlorfenapyr has been monitored since the 1997--1998 growing season. Resistance was first detected in the 2001--2002 season and then increased quickly in both level and proportion of resistant strains detected. In response, the resistance management strategy for chlorfenapyr use in cotton was altered and now recommends a further restriction of use from two to one spray per season. There was no evidence of negative cross-resistance to the pyrethroid bifenthrin, but chlorfenapyr was associated with an undefined negative cross-resistance.