Organophosphate insecticides and acaricides antagonise bifenazate toxicity through esterase inhibition in Tetranychus urticae.
BACKGROUND
Bifenazate is a carbazate acaricide known for its potency, particularly against tetranychid mite species such as the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). It was recently shown that the compound needs to be activated by an S,S,S-tributyl-phosphorotrithioate (DEF)-sensitive mechanism in spider mites to display full acaricidal efficacy. The ability of well-known organophosphates and carbamates to inhibit the activation of bifenazate and thus compromise its acaricidal potential was tested.


RESULTS
Esterase activity determined in vivo after pre-exposure of mites with organophosphates and carbamates revealed--depending on the compound--varying esterase inhibition nicely correlated with the ability of the individual compound to antagonise bifenazate action on mites.


CONCLUSIONS
The findings illustrate that organophosphates and carbamates interfere with bifenazate efficacy, most probably by inhibiting carboxylesterases responsible for the activation of the pro-drug. As a result of the strong antagonism, mixtures of bifenazate with carbamates or organophosphates should not be used under field conditions. Moreover, there exists a real threat in repeatedly applying organophosphates and bifenazate. The present study again illustrates how important mode of action information is for the proper planning of resistance management strategies.
Van Leeuwen
Thomas
T
Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Ghent, Belgium. thomas.vanleeuwen@ugent.be
Van Pottelberge
Steven
S
Nauen
Ralf
R
Tirry
Luc
L
D000818:Animals; D001681:Biological Assay; D002219:Carbamates / Q000037:antagonists & inhibitors*; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors*; D005260:Female; D006834:Hydrazines / Q000037:antagonists & inhibitors*; D007305:Insecticide Resistance; D007306:Insecticides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010755:Organophosphates / Q000494:pharmacology*; D010571:Pest Control; D040102:Tetranychidae / Q000187:drug effects* / Q000201:enzymology
D002219:Carbamates; D006834:Hydrazines; D007306:Insecticides; D010755:Organophosphates; C508134:bifenazate; D002265:Carboxylic Ester Hydrolases