Italian ryegrass is a common weed in arable crops
John Cussans
Weeds resistant to the herbicide glyphosate have been discovered in the UK for the first time. Italian ryegrass, a prevalent weed in the country, has shown resistance to the chemical on a farm in Kent.
Glyphosate has played a crucial role in promoting regenerative agriculture practices among farmers, as stated by John Cussans, a weed management expert at ADAS. Tests conducted by his team in a greenhouse confirmed the resistance of the plants to glyphosate.
This development poses a significant challenge to the farming system’s transition, according to Cussans. Glyphosate is primarily used in the UK to clear fields of all vegetation before sowing seeds, enabling farmers to avoid soil-damaging ploughing.
The use of glyphosate aligns with the principles of regenerative agriculture, which emphasizes minimal soil disturbance, crop rotation, and maintaining ground cover. Helen Metcalfe from Rothamsted Research highlights the environmental benefits of glyphosate, citing its low toxicity and support for practices like minimum tillage that enhance soil health.
Weed infestation is a major concern for farmers, with Paul Neve from the University of Copenhagen noting that weeds cause more crop yield loss than insect pests or pathogens. Glyphosate-resistant weeds, including Italian ryegrass, have emerged globally, posing challenges for farmers in countries like the US and Argentina.
Despite the prevalence of glyphosate resistance, Neve points out that the issue has not escalated dramatically since its initial discovery 30 years ago. Preventive measures such as equipment cleaning and diversification of weed control methods can help slow down the spread of resistant weeds.
Metcalfe emphasizes the importance of farmers adopting multiple weed control strategies beyond glyphosate to mitigate the impact of resistant weeds on crop yields. By implementing alternative methods, profitability can begin to recover within five to ten years.
Cussans’s team intensified surveillance efforts in the UK, testing over 300 Italian ryegrass samples in 2018. He believes that the evolution of resistance likely occurred on the Kent farm rather than being introduced from external sources.
The delayed emergence of resistance in the UK compared to other countries may be attributed to the absence of genetically modified or conventionally bred crops with glyphosate resistance. Such crops allow glyphosate application during crop growth, providing continuous weed control.
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