Acaricide resistance of the two-spotted spider mite (Tetranychus urticae) in Washington hops and mint

The two-spotted spider mite (Tetranychus urticae) is a dangerous pest to many agricultural crops. In the Pacific Northwest, T.urticae is of particular importance because infestation damage threatens yield loss of specialty perennial crops, such as hops and mint. Moreover, mites are well documented to develop resistance, leading to complications in pest management. In our study, we investigate the level of acaricide resistance of T.urticae in Washington hops and mint in effort to improve management strategies. First, we identify baseline dose response curves of spider mite populations susceptible to three acaricides (abamectin, bifenazate, and bifenthrin). Next, we develop discriminating doses of acaricides that can be used to rapidly identify the prevalence of tolerance or resistance in a spider mite population. Finally, we test select field populations of spider mites from hop yards and compare their dose response curves to known susceptible and resistant mite populations.