Glyphosate resistance found in UK
Growers are urged to closely follow glyphosate stewardship advice after the discovery of a resistant Italian ryegrass on a farm in Kent. This is the first field population of any weed to have glyphosate resistance in the UK, explains the Weed Resistance Action Group (WRAG).
“Glyphosate is probably the most important herbicide for UK farmers and there is no obvious replacement hence any case of resistance is concerning,” says John Cussans, principle weed science consultant at ADAS, who led the research.
“But we must retain perspective; it’s resistance in one weed species on one farm, it is not a widespread problem yet. For context, over the period 2018 to 2023 we have collated data for samples of Italian ryegrass that were submitted for standard resistance tests. They have been screened with glyphosate, and we have not found a single resistant sample. This single case does, however, serve as a firm reminder of the importance of glyphosate stewardship otherwise we are likely to see more cases.”
Reducing resistance risk
There are fundamental stewardship steps that all those using glyphosate need to take. Moreover, farmers with higher risk systems must be extra vigilant and consider adjusting their approach to reduce selection pressure for glyphosate resistance.
“From the cases we know about, the two main risk factors are Italian ryegrass populations and little or no mechanical weeding through cultivation in the system. There are many good reasons for a reduced cultivation system, but for all the benefits, more focus on glyphosate stewardship is one of the trade-offs in such a system.
“Of course, cultivation doesn’t give farmers a free pass. They should also follow good stewardship practice, but have more tools available,” says Mr Cussans.
Use a sufficient dose of glyphosate to kill all target weeds because any weed which survives a glyphosate application is a potential resistance risk. Selecting the right rate for the size and hardest to kill species in the weed spectrum is the starting point. Correct application technique ensures the required rate reaches the intended target.
Follow best practice
There are many aspects of sprayer setup, maintenance and operation that can influence application quality. Nozzle choice, forward speed of no more than 12kmh and water quality are three of the most important.
At the time of application, weeds should be actively growing to allow translocation of glyphosate throughout the plant for effective control. Do not apply to plants under stress such as waterlogging, drought or during very cold weather. Also, avoid applications during the stem extension phase of growth because the glyphosate is translocated to the growing tip but not to the roots leading to potential regrowth.
Full details on how to get the best from glyphosate and combat resistance can be found HERE.
