Incidence of pyrethroid-resistant oilseed rape pests in Germany.
BACKGROUND
Failures in pollen beetle control using pyrethroids since 2005 indicated pyrethroid resistance in Germany. Therefore, resistance monitoring using bioassays was established in Germany for oilseed rape pest insects.


RESULTS
The spread and intensity of pyrethroid resistance of Meligethes aeneus increased from 2005 onwards, with no sensitive samples left in any region of Germany in 2011. Sensitivity also declined for the newly introduced actives bifenthrin, etofenprox (both class-I pyrethroids) and tau-fluvalinate; all three claimed to be less affected by resistance, although there was no clear cross-resistance to lambda-cyhalothrin (class-II pyrethroid). In the German region with the longest tradition and high intensity of oilseed rape production, pyrethroid resistance of Psylliodes chrysocephala and Ceutorhynchus obstrictus, with resistance factors of up to 81 and 140 respectively, was detected.


CONCLUSIONS
The intensive use of only one mode of action for many years is risky, because even pest insects with a low intrinsic resistance risk may develop resistance. Therefore, resistance strategies need to include several control options for pest insects needing regular treatments.
Institute for Plant Protection in Field Crops and Grassland, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany. udo.heimbach@jki.bund.de
Udo
U
Heimbach
Andreas
A
Müller
D000818:Animals; D029741:Brassica rapa / Q000469:parasitology*; D001517:Coleoptera / Q000187:drug effects; D005858:Germany; D007300:Insect Control; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*
D007306:Insecticides; D011722:Pyrethrins