title: Esterase-mediated bifenthrin resistance in a multiresistant strain of the two-spotted spider mite, Tetranychus urticae.
abstract: A field-collected multiresistant strain of Tetranychus urticae Koch exhibiting high resistance to bifenthrin was investigated in comparison with a susceptible laboratory strain. The esterase inhibitor S,S,S-tributyl-phosphorotrithioate (DEF) was able strongly to synergise bifenthrin toxicity in the resistant strain. Optimal conditions for determining esterase activities in T. urticae were determined, and a higher esterase activity towards several artificial substrates was found in this resistant strain, which had a preference for hydrolysing 4-nitrophenyl butyrate. Bifenthrin was able to bind the active centres of T. urticae esterases in vitro, as was determined after competition experiments by a Dixon plot, revealing a higher affinity of bifenthrin in the resistant strain. Bifenthrin-hydrolysing activity in the resistant and susceptible strains was examined in vitro and quantified with gas chromatography. A 7.2-fold higher metabolising rate was found in the resistant strain.
authors.affiliation: Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium. Thomas.vanleeuwen@ugent.be
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Leeuwen
authors.forename: Luc
authors.initials: L
authors.lastname: Tirry
mesh_terms: D000818:Animals; D001681:Biological Assay; D004950:Esterases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D013696:Temperature; D040102:Tetranychidae / Q000187:drug effects* / Q000201:enzymology*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; C099952:bifenthrin; D004950:Esterases