Growers are being asked to send suspected pyrethroid-resistant cabbage stem flea beetle (CSFB) samples this harvest to Rothamsted Research for resistance analysis.

Following last year’s restriction, oilseed rape (OSR) seed treated with neonicotinoids cannot be planted this autumn and foliar-applied pyrethroids will now be the main treatment option to protect OSR during the first 6-8 weeks of growth from CSFB attack.

Following reports of knock-down resistance (kdr) to pyrethroids in CSFB in Germany and suggestions from UK growers that pyrethroids are failing against CSFB in the UK, HGCA has commissioned research to investigate the issue.

As part of this work, Rothamsted Research is calling for growers to send CSFB populations, where resistance is suspected, to them for analysis to help detect any potential resistance issues in the UK.

Dr Stephen Foster of Rothamsted Research said: “We are looking to see if the kdr mutation is present in UK CSFB populations and, assuming it is, we will then work to quantify resistance levels.

“As we need good samples with a high number of live beetles, we are asking growers to sample around harvest because beetles are found in large numbers at this time.

“To help growers, we have produced some simple sampling guidelines which are available from the HGCA website.

“With many more growers considering pyrethroid applications this autumn as a consequence of the neonicotinoid restriction, it is essential that we all work together to understand and manage any potential resistance threat.”

The CSFB resistance project is part of a package of research commissioned by HGCA in response to the restrictions.

Caroline Nicholls, HGCA Research and KT Manager, said: “We have also asked Rothamsted Research to develop a laboratory assay to test the potential of peach–potato aphids to transmit turnip yellows virus (TuYV), in addition to screens already underway to detect known insecticide resistance mechanisms.

“We have also funded ADAS to investigate how much shot hole damage OSR seedlings can tolerate so we can make sure growers are working with the best spray thresholds for CSFB.

“Where possible, results from our research will be made available in time to help growers adapt their pest control strategies for OSR this autumn.

Download the sampling guidelines here. Further information is available from www.hgca.com/neonics