The Weed Resistance Action Group (WRAG) has confirmed the first case of full rate glyphosate resistance in the UK within a weed population.
Significantly, a single field population of Italian ryegrass has been identified, which is resistant to the herbicide at the maximum label rate.
This finding has been rigorously investigated and the population has been re-sampled and re-tested.
This is the first such fully documented case in the UK. The situation represented a high risk and although several other cases were investigated, these all turned out to be well-controlled by well-applied field rates.
Testing for glyphosate resistance
Since the summer of 2019, over 300 seed samples have been screened by ADAS and the UK’s Institute of Agricultural Botany.
No evidence of glyphosate resistance has been identified within this extensive survey.
Several other populations were identified as high risk, but in every other case, following further investigation and re-sampling, no indication of glyphosate resistance was detected.
A very small number of other cases are still under investigation.
In response to this development, WRAG is highlighting its guidelines on how growers can best minimise the rise of glyphosate resistance becoming a more widespread challenge.
Steps to take
Steps that can be taken by farmers include the use of effective crop rotations, the thorough disturbance of a soil profile in order to kill existing weeds, using a mix of herbicides, limiting the use of glyphosate to no more than one application per crop cycle and targeting weeds at the correct growth stage.
It is also imperative that growers use glyphosate at full label application rates.
WRAG is also confirming that an over-reliance on a limited group of herbicide modes of action has accelerated the development of herbicide-resistant grass weeds, particularly blackgrass.
Glyphosate is one of the most frequently used herbicides in the UK and Ireland, including in annual and perennial crops and non-cropped areas.
Up to this point, most confirmed cases of glyphosate resistance in Italian ryegrass have been in North and South America.
There have been cases of glyphosate resistance in Europe (2006 in Spain and 2012 in Italy). However, it’s notable that the situation in both countries has not escalated resulting in a widespread problem.
The European Commission has considered banning the use of glyphosate entirely on a number of occasions. However, it is an approach that has been strongly opposed by farming organisations across Europe.
