Managing herbicide resistance

In 2025, the first case of glyphosate resistance in Italian ryegrass in the UK was identified. This discovery re-enforced the need to adopt an integrated approach to grass weed management and to select and effectively utilise a range of tools available to manage grass weeds on farm. The need for an integrated approach to grass weed management applies to all grass weeds (including blackgrass and wild oats, for example) as well as Italian ryegrass.

Once resistance occurs, it’s not reversible and it can make grass weeds much more difficult to manage. That’s why, as a cereal grower, you should aim to control weeds with resistance in mind.

Why does herbicide resistance happen?

Resistance occurs when a weed survives a rate of herbicide which would ordinarily kill it. This was the case with the population of Italian ryegrass in Kent (as reported above), where field label rates of glyphosate failed to provide control. This resistance is then passed down genetically causing a growth in resistant weed populations.

Spotting herbicide resistance

Some early signs of herbicide resistance include:

• A decline in weed control that occurs over several seasons.
• Seeing healthy weeds growing alongside dead plants from the same species.
• Poor control of a susceptible species when other weeds are controlled. 

Industry best practice recommendations 

The Weed Resistance Action Group (WRAG) has issued guidelines with regard to glyphosate stewardship. It is asking growers to:

• Prevent survivors: avoid repeat applications to surviving plants.
• Maximise efficacy: apply the right dose rate to kill all target weeds (reduced rates increase the risk of reduced efficacy), at the right timing (when weeds are actively growing, avoiding stem extension growing phase), in the right conditions (do not apply to plants under stress from waterlogging, drought, and very cold weather).
• 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 manufacture.

Refer to the WRAG website for more information and the latest updates.

Syngenta is committed to supporting UK farmers manage grass weeds and we have a range of chemical and cultural tools available; including:

• Tried and trusted herbicides such as AXIAL^® Pro.

• Application advice to maximise effectiveness of herbicides applications.

• Digital support tools such as the Syngenta Portal.

• Competitive HYVIDO^® winter barley varieties to suppress weeds.

We continue to invest and collaborate with industry partners such as ADAS to trial novel ideas to control grass weeds on farm to support UK farmers and sustainable production.