Growers are being urged to monitor pyrethroid resistance in cabbage stem flea beetles (CSFB) this harvest by sending samples in for testing to Rothamsted Research.

Following the restriction on neonicotinoid seed dressings, foliar-applied pyrethroids will provide the main treatment against CSFB attacks.

However, following reports of knock-down resistance to pyrethroids being found in Germany and suggestions of foliar-based sprays failing UK growers, concerns over the control of the pest have intensified.

See also: Neonicotinoids ban makes pest control harder for OSR

Independent crop expert and entomologist Alan Dewar, says with more oilseed rape growers considering pyrethroid applications this autumn as a consequence of the neonicotinoid restriction, the importance of testing will be huge.

The seed dressing had previously given protection during the first six to eight weeks preventing the beetles from feeding on the oilseed rape cotyledons and laying eggs.

“This summer will therefore be vital to measure the extent of resistance so that appropriate advice can be given on their control,” he explains.

Dr Dewar points out that if widespread resistance is found then growers could be wasting time and money applying pyrethroids.

“Other strategies may also need to be employed, for example, increasing seed rates,” he explains.

Rothamsted Research are calling for samples to be sent in for testing during harvest time, when high numbers can be found as grain begins to enter the store.

The CSFB-resistance project is part of a package of research commissioned by HGCA, which also includes further work into the potential of peach-potato aphids to transmit turnip yellows virus.

Growers can find out more on the HGCA website which also provides simple sampling guidelines and information on where samples can be sent in.