As featured in Arable Farming Magazine
Protecting the efficacy of glyphosate
by Arable Farming August 2020
An AHDB-funded project nearing completion has sought to understand and quantify the risk of glyphosate resistance developing in UK grass-weed populations. Andrew Blake reports.
Preserving glyphosate herbicide’s efficacy on grass-weeds has been the aim of five years of AHDB-backed research which comes to a close in September 2020. The ability of weeds in some parts of the world to survive glyphosate treatment underlies the £0.5 million project*.
ADAS research scientist Lynn Tatnell, who has led the work, explains: “We needed to be sure that the risk of glyphosate resistance developing in UK grass-weeds was understood and could be quantified.”
Resistance to the world’s most widely used herbicide was first identified in rigid ryegrass in Australia as long ago as 1996, according to the International Survey of Herbicide Resistant Weeds. Since then resistance in a wide range of weeds, both grasses and broad-leaved types, has been recorded in many countries.
The reasons have been over-reliance on the chemical and repeated use since it was introduced nearly 50 years ago, believes Mrs Tatnell.
Increasing use of glyphosatetolerant crops since the mid-1990s has inevitably led to an increase in glyphosate-resistant weeds, she adds.
“The clear lesson is that dependence on glyphosate alone is inappropriate.
“The risk of resistance in the UK is real if we continue to use it in the way we have been.
“It is important that we retain this highly valuable herbicide and don’t abuse it. By understanding how to get the best out of it, the industry will retain it for as long as possible because we won’t be causing resistance to occur in the first place.”
Encouragingly the offer of free tests for ‘difficult to control’ grass-weed populations throughout the project’s life have attracted very few samples, she says: “All were well controlled in a dose response glasshouse test.
“This is a good thing reflecting perhaps what’s happening in the field, and that hopefully in the UK we’re still getting good control.”
Complacency must be avoided, she urges, and the project has resulted in key messages. (See the panel above).
Key messages from the research
- Optimising the herbicide treatment is essential to reduce the resistance risk
- Do not cut corners – keep the rate up and apply at the correct growth stage
- Monitor suspected resistant patches and if in doubt remove small areas before they spread. Carry out testing on seeds and plants
- *AHDB project
Managing the resistance risk to retain long-term effectiveness of glyphosate for grass-weed control in
UK crop rotations
- October 1, 2015 – September 30, 2020
- Cost: Total £500,000 (AHDB £250,000)
- Project partners: Albaugh, FMC (Headland), Monsanto (Bayer) and Nufarm £40,000 each
- Agrii, Agrovista, Frontier, Hutchinsons and Syngenta – all in-kind contributions including field sites