The UK does not fare too badly on the world stage for resistant weeds, but the resistant species that are present here are causing considerable problems in the
In the UK there are 16 known resistant weed species that have developed resistance to nine herbicide modes of action, with most cases coming from cereal cropping situations, according to Dr David Comont, research scientist at Rothamsted Research.
In broad-leaved species, resistance levels are still relatively low, but resistant grass-weeds, including wild oats, ryegrass and particularly blackgrass, are now becoming very prevalent, particularly across England, says Dr Comont.
“Black-grass is reported as the number-one issue on arable farms. In part, what is causing that is some of the grass-weed populations have evolved resistance to multiple modes of action simultaneously.
“Recent studies have found UK brome populations may be developing herbicide resistance and populations of ryegrass are showing the first signs of reduced sensitivity to flufenacet.
Black-grass is also now showing the first signs of reduced sensitivity to glyphosate. We know from other countries that glyphosate resistance can evolve from other species.”
Dr Comont says the situation is down to a lack of diversity.
“There are fewer chemicals, fewer mixed farms and narrower arable rotations, with mainly autumn-sown crops. This helps autumn germinating weeds such as black-grass to flourish. We then become reliant on using herbicides alone.”