Guidelines issued on weed resistance risks

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Guidelines from WRAG (Weed Resistance Action Group) have been published by the Agriculture and Horticulture Development Board (AHDB) in response to the ‘real risks’ of glyphosate resistance developing in UK weeds.

While WRAG and AHDB emphasise there are currently no known cases of glyphosate resistance in UK weeds, the guidelines build on global experience to help growers maintain the effectiveness of glyphosate as a weed control option.

Glyphosate has been around for 40 years and has become one of the most frequently used herbicides across UK crop production.

Increasing resistance to selective herbicides – especially in grassweeds within UK arable cropping systems – and a reduction in available chemistry means the pressure to use glyphosate as a stale seedbed management tool, in particular, is increasing and it is vital to retain its effectiveness.

Without the use of glyphosate, a potential loss of yield and quality would occur across all cropping systems. In particular, it has been estimated that a 20% yield loss would occur without the use of glyphosate pre-drilling.

James Clarke, WRAG Chair and Science and Business Development Manager at ADAS, said: “Globally, 31 weed species have been reported to have developed resistance to glyphosate, so WRAG drafted the guidelines to help agronomists and growers maintain UK efficacy.

“A number of high-risk practices are being increasingly deployed on UK farms which could drive the evolution of glyphosate resistance in UK weeds – including multiple glyphosate applications, sublethal doses and suboptimal application timing – and we wanted to be proactive in highlighting the risks and promoting best practice.

“We have pulled together the latest information, including lessons from global experience, to present key points to ensure the efficacy of this important active in weed control is maintained.”

The new Minimising the risk of glyphosate resistance guidelines include four simple and key messages, supported by more detailed evidence and guidance.

These are:

Prevent survivors: Avoid repeat applications to surviving plants

Maximise efficacy: Apply the right dose rate (reduced rates increase the risk of reduced efficacy), at the right timing, in the right conditions

Use alternatives: Use non-chemical options (such as cultivation), where practical, and use other herbicides in sequence

Monitor success: Remove survivors and report potential resistance issues to your advisor and/or the product manufacturer.