Genetic and biochemical analysis of a laboratory-selected spirodiclofen-resistant strain of Tetranychus urticae Koch (Acari: Tetranychidae).
BACKGROUND
Spirodiclofen is a selective, non-systemic acaricide from the new chemical class of tetronic acid derivatives. In order to develop strategies to minimise resistance in the field, a laboratory-selected spirodiclofen-resistant strain of the two-spotted spider mite, Tetranychus urticae Koch, was used to determine genetic, toxicological, biochemical and cross-resistance data.


RESULTS
Selecting for spirodiclofen resistance in the laboratory yielded a strain (SR-VP) with a resistance ratio of 274, determined on the larval stage. The egg stage remained far more susceptible. No cross-resistance was found against other established acaricides, except for spiromesifen. Based on synergist experiments and enzyme assays, it appeared that especially P450 monooxygenases, but also esterases and glutathione-S-transferases, could be involved in the metabolic detoxification of spirodiclofen. Genetic analysis showed that the resistance is inherited as an intermediate trait under control of more than one gene.


CONCLUSIONS
Resistance to spirodiclofen exceeded by far the recommended field rate. A good acaricide resistance management programme is necessary to prevent fast resistance build-up in the field. Spirodiclofen can be used in alternation with most established acaricides, except for other tetronic acid derivatives. Without selection pressure, resistance tends to be unstable and can decrease in the presence of susceptible individuals owing to the intermediate, polygenic inheritance mode.
Van Pottelberge
Steven
S
Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Van Leeuwen
Thomas
T
Khajehali
Jahangir
J
Tirry
Luc
L
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D012641:Selection, Genetic; D013141:Spiro Compounds / Q000494:pharmacology*; D040102:Tetranychidae / Q000187:drug effects* / Q000235:genetics*
D007306:Insecticides; D013141:Spiro Compounds; C508135:spirodiclofen; D015107:4-Butyrolactone