PLoS ONE (2015) 10 (12 - e0146045)

Dorte H. Højland, Ralf Nauen, Stephen P. Foster, Martin S. Williamson and Michael Kristensen (2015)
Incidence, spread and mechanisms of pyrethroid resistance in European populations of the cabbage stem flea beetle, Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae)
PLoS ONE 10 (12 - e0146045)
Abstract:
Background
Cabbage stem flea beetle (CSFB), Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae) is a major early season pest of oilseed rape throughout Europe. Pyrethroids have been used for controlling this pest by foliar application, but in recent years control failures have occurred, particularly in Germany due to the evolution of knock-down resistance (kdr). The purpose of this study was to investigate the incidence and spread of pyrethroid resistance in CSFB collected in Germany, Denmark and the United Kingdom during 2014. The level of pyrethroid resistance was measured in adult vial tests and linked to the presence of kdr genotypes.
Results
Although kdr (L1014F) genotypes are present in all three countries, marked differences in pyrethroid efficacy were found in adult vial tests. Whereas Danish CSFB samples were in general susceptible to recommended label rates, those collected in the UK mostly resist such rates to some extent. Moderately resistant and susceptible samples were found in Germany. Interestingly, some of the resistant samples from the UK did not carry the kdr allele, which is in contrast to German CSFB. Pre-treatment with PBO, prior to exposure to lambda-cyhalothrin suggested involvement of metabolic resistance in UK samples.
Conclusion
Danish samples were mostly susceptible with very low resistance ratios, while most other samples showed reduced sensitivity in varying degrees. Likewise, there was a clear difference in the presence of the kdr mutation between the three countries. In the UK, the presence of kdr genotypes did not always correlate well with resistant phenotypes. This appears to be primarily conferred by a yet undisclosed, metabolic-based mechanism. Nevertheless our survey disclosed an alarming trend concerning the incidence and spread of CSFB resistance to pyrethroids, which is likely to have negative impacts on oilseed production in affected regions due to the lack of alternative modes of action for resistance management purposes.
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Full text of article
Database assignments for author(s): Michael Kristensen, Ralf Nauen, Martin S. Williamson, Steve Paul Foster

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Psylliodes chrysocephala	Rape/canola (Brassica napus)	Denmark
	Psylliodes chrysocephala	Rape/canola (Brassica napus)	Germany
	Psylliodes chrysocephala	Rape/canola (Brassica napus)	United Kingdom