Minimising the Risk of Glyphosate Resistance

In light of this year’s discovery of the first field population of any weed to have developed glyphosate resistance in the UK, how can the risk of glyphosate resistance in arable cropping systems be minimised moving forward?

Key Points

· Glyphosate is a non-selective foliar-acting herbicide used across all UK crop production systems.

· Since 1990, there has been a significant increase in the use of glyphosate on cereal crops in the UK.

· The discovery of the first field population of any weed to have developed glyphosate resistance in the UK (January 2025; annual Italian ryegrass) emphasises the need for integrated control strategies.

· The Weed Resistance Action Group (WRAG) provides guidelines to minimise the risk of glyphosate resistance, including preventing survivors, maximising efficacy, using alternatives, and monitoring success.

Background Information

Glyphosate is one of the most frequently used herbicides in the UK across all crop production systems, including annual and perennial crops, and non-cropped areas. It is a non-selective foliar-acting herbicide with no soil residual activity, and is used to control weeds post-emergence. In cereal crop production, glyphosate is used regularly to control a range of weeds as part of a stale seed bed technique pre-drilling.

Glyphosate Usage

The stale seed bed technique allows newly emerged grassweeds to be removed prior to crop drilling, which reduces the pressure on in-crop herbicide programmes. As such, it is a vital component of weed management control regimes, with glyphosate applied when target weeds are at their very early growth stages to improve the likelihood of successful control. Over the past 30 years (1990-2020), there has been a significant and sustained increase in the use of glyphosate on cereal crops in the UK (Figure 1), and there are now many reports of multiple glyphosate applications pre-drilling between every crop in the rotation, year-on-year. Although the resistance risk from a single application is typically low, multiple glyphosate applications between every crop in the rotation could contribute to the development of resistant weed populations, and therefore may not be a sustainable management strategy in the long-term1.

Figure 1. Glyphosate use on UK cereal crops. Data shows the total UK cereal crop area treated with glyphosate (1990-2020). Data sourced from Pesticide Usage Surveys2.

Several factors have contributed to sustained increases in glyphosate use, including its efficacy across a broad range of weeds, and its cost effectiveness. In addition, in recent years, regenerative agriculture techniques have become more commonplace across the UK as part of the Agricultural Transition Plan and schemes within it, such as the Sustainable Farming Incentive, with farmers and growers altering agricultural practices to conserve and rehabilitate the environment, while continuing to produce food. One of the core components of regenerative agricultural practice is limiting disturbance to the soil to protect and improve soil structure, build soil organic matter, and reduce carbon release into the atmosphere. Glyphosate use facilitates the adoption of such practices by minimising the need for weed (and cover crop) control by soil cultivation or disturbance (e.g. ploughing, tilling)3. As such, increased adoption of regenerative agriculture practices across the UK may have, in part, driven recent increases in glyphosate use, though not in isolation4.

Glyphosate Resistance

Over the past 20 years, there has been a rapid increase in herbicide resistant grassweeds within arable cropping systems – particularly black-grass5. This is due to various factors, but has been driven primarily by a reduction in the availability of different herbicide products as a result of regulatory policy changes, a lack of new herbicides on the market, and consequent over reliance on a limited group of modes of action.

Recent patterns of glyphosate use (Figure 1) have led to a heightened risk of glyphosate resistance emerging in arable cropping systems. Worldwide, there have been cases of glyphosate resistance reported, which suggest that reliance on the use of glyphosate alone, without mitigation measures (e.g. cultural and rotational control), is a key driver for the development of resistance. As of December 2024, reduced sensitivity had been detected in Italian ryegrass and sterile brome populations in the UK6.

Glyphosate Resistance in the UK

The Weed Resistance Action Group (WRAG) reported on 10th January 2025 the discovery of the first field population of any weed to have glyphosate resistance in the UK7. The population of glyphosate-resistant annual Italian ryegrass (Lolium multiflorum) was found on a farm in Kent, and is believed to have developed in situ, rather than being introduced via contaminated seed or equipment. The resistant population has now been eradicated, and control measures are in place on the farm to prevent seed dispersal8.

Subsequent investigations tested three additional populations of annual Italian ryegrass from Somerset, Essex, and North Yorkshire. Two of these demonstrated significantly reduced control from appropriate doses of glyphosate, while the third population showed decreased glyphosate sensitivity. All of these cases originated from high-risk scenarios (e.g. in which large annual Italian ryegrass plants were surviving high rates of glyphosate prior to drilling spring crops in reduced tillage systems9,10) and have underscored the importance of glyphosate stewardship to prevent further development of resistance in the UK.

Risk Factors for Glyphosate Resistance

Scenarios in UK agriculture that present the highest risk of glyphosate resistance are: (1) in annual arable crops, particularly where glyphosate is used to manage grass weeds that have developed resistance to numerous selective herbicides; and (2) in perennial crops and amenity areas, where glyphosate is used on both annual and perennial weeds, with limited alternative modes of action available. The WRAG summarises various agronomic factors and their risk profiles for glyphosate resistance, outlined in Table 11.

Table 1. Risk factors for glyphosate resistance. Information sourced from WRA

Practical Recommendations

Various actions can be taken to minimise the risk of glyphosate resistance in arable cropping systems. The WRAG produces guidance on pesticide resistance issues to help protect crops and the long-term efficacy of herbicides1. It splits its guidance on glyphosate use into four key pillars, as detailed below. It is vital to work with your agronomist to implement these WRAG guidelines to minimise the risk of resistance on-farm.

1. Prevent Survivors: Avoid repeat applications to surviving plants.

2. Maximise Efficacy: Minimise the number of applications while maximising efficacy by using the right dose for the target weed on newly emerged plants, and use the manufacturer’s recommended dose rate. Reduced rates that allow more surviving plants may encourage the development of resistance. Apply in suitable environmental conditions (e.g. 15-25°C, and at least 6 hours before rainfall).

3. Use Alternatives: Ensuring diversity in grass-weed control is fundamental to glyphosate stewardship. Ensure use is supplemented by sufficient non-chemical controls (e.g. cultivation, crop rotation) to kill surviving plants, and use herbicides of different modes of action (in sequence or mixture) as recommended.

4. Monitor Success: Remove surviving plants to prevent seed spread, and report suspected survivors to your agronomist, crop protection adviser, and / or product manufacturer for resistance testing.

Concluding Remarks

The discovery of glyphosate resistant and sensitive weed populations in the UK emphasises the need for integrated control strategies. In March 2025, the UK government launched the Pesticides National Action Plan, aiming to reduce the environmental impact of pesticides by 10% over the next five years11,12. The plan promotes Integrated Pest Management (IPM) strategies, and encourages the adoption of nature-friendly farming techniques to mitigate pesticide resistance and protect ecosystems. By following the WRAG guidelines and adopting a diverse IPM approach to weed control, farmers and growers can minimise the risk of glyphosate resistance and ensure the long-term efficacy of herbicides in arable cropping systems.

References

1. WRAG (2021) Guidelines for minimising the risk of glyphosate resistance in the UK

2. Pesticide Usage Surveys

3. Neve et al. (2024) Current and future glyphosate use in European agriculture

4. Pullman (2023) Glyphosate use rises in UK farming while overall pesticide use falls

5. Hull et al. (2014) Current status of herbicide-resistant weeds in the UK

6. ADAS (2024) Weed management and resistance (AHDB Agronomy Conference 2024)

7. Farmers Weekly (2025) First case of glyphosate resistance confirmed on UK farm

8. NFU (2025) Glyphosate resistance – what you need to know

9. NFU (2025) First glyphosate resistant weeds in UK highlight importance of stewardship

10. WRAG (2025) Weed Resistance Action Group confirms first cases of glyphosate resistance in UK

11. Defra (2025) Nature boost: Government launches first action plan on pesticides in a decade

12. Defra (2025) UK Pesticides National Action Plan 2025