Rothamsted Research says it has detected clear signs that blackgrass is developing reduced sensitivity to glyphosate in the field, and that over-reliance on the herbicide should be avoided.

The researchers have developed a method of predicting the risk of resistance before it occurs in the field, using a novel combination of field monitoring, glasshouse experiments and classical genetics.

Commenting on a study into the use of glyphosate in blackgrass, weed ecologist Dr David Comont said the work provided an early warning to the UK farming industry that over-reliance on glyphosate is likely to lead to resistance.

“We found evidence that a number of blackgrass populations are responding to glyphosate use by evolving reduced sensitivity to this herbicide in the field. Crucially, our results show this happening before high levels of resistance have evolved, whilst there is still time to delay or prevent this resistance.”

Dr Paul Neve, head of the Weed Ecology and Evolution research group at Rothamsted, adds that increased usage – glyphosate applications in the UK have risen eightfold over the last three decades – is driving the evolution of resistance.

The study, in collaboration with the University of Sheffield, collected blackgrass seed from 132 fields across 11 English counties from Hertfordshire to Yorkshire, together with field and crop management records.

The results were published in the New Phytologist journal.