Dr David Comont, Rothamsted: Our new early warning system has found blackgrass evolving resistance to glyphosate

Predicting the risk of resistance before it occurs in the field will be vital to future control says Rothamsted’s Dr David Comont

I have to confess a sneaking admiration for blackgrass. It may be the bane of many a cereal farmer, but as an ecologist, it’s hard for me not to be impressed by its resilience and adaptability.

Now it seems to be changing again as we have detected early signs of resistance evolving to one of its main control agents, the weed killer glyphosate.

Worryingly, these latest findings show that this ubiquitous farmland weed could soon become uncontrollable, as glyphosate is one of the last lines of defence against what has been described as a weed “epidemic”. If no new measures to combat blackgrass emerge, then falling yields of crops such as wheat would likely lead to higher prices in the shops.

The results come from a new ‘early warning system’ that we have developed at Rothamsted that aims to identify those weed populations that are close to becoming herbicide resistant.

Resistance to pesticides – like the antibiotic resistance crisis in healthcare – is a major problem for farmers across the world, and once resistance has evolved in a pest population, is almost impossible to reverse. Glyphosate is one of the few herbicides that blackgrass isn’t already resistant to, and according to a recent study, it’s use by UK farmers has risen eight-fold in the last 30 years. It now accounts for a quarter of all herbicide sales globally.

Resistance to glyphosate would have considerable impacts on farmers, with an estimated 10-12% reduction in UK cereal and oilseed production, potentially costing over £500 million per year. but if spotted early, resistance could still be avoided with smarter use of herbicides and other control methods.

So, we need to develop ways to detect the early signs of resistance emerging, and identify alternative control strategies which can be used to help fight this weed.

That way we can intervene before resistance becomes a major problem on farms.

The results of our recent study, published in the journal New Phytologist, demonstrate a completely new approach that combines field monitoring, glasshouse experiments, and classical genetics to predict the risk of resistance before it occurs in the field.

Working with our collaborators at the University of Sheffield, we collected blackgrass seed from 132 farmer’s fields across 11 English counties – from Hertfordshire in the south to Yorkshire in the north – in addition to collecting information on how the field was farmed over the previous seven years or so.

More than 16,000 seedlings were grown in glasshouses, and 400 new seed lines were produced by cross breeding, all tested for their sensitivity to glyphosate

We showed that the degree of sensitivity was something plants inherited from their parents, and that the variation in sensitivity between populations was a result of historical glyphosate exposure – both prerequisites for pesticide resistance evolution.

Taken together these results confirm that blackgrass populations can evolve reduced sensitivity to glyphosate on repeated exposure in farmers’ fields.

Crucially, this type of early detection can only take place where we have large-scale systematic monitoring of blackgrass populations in the field. So, we are developing a programme of systematic surveillance, to catch the early signs of these changes taking place. With our partners at Sheffield University, we are now teaming up with partners Hummingbird technologies, precision decisions and IBM research UK to systematically monitor this weed across England.

By flying drones over farmers’ fields, we’ll be able to more rapidly survey infestations of this pernicious weed, and through our partnership with IBM, we’ll also be able to leverage cutting edge ‘artificial intelligence’ computing. It’s hoped that this type of monitoring will help us to hone in on the techniques which can still work to control blackgrass in the field.

Over the next few seasons, working with our new project partners, we will continue to improve our monitoring and understanding of this weed, with the hope that one day we’ll be able to say that blackgrass’s days as the preeminent arable weed are numbered.

Visit the Rothamsted stand at Croptec 2019 to talk to our experts and learn more about our research on blackgrass.