In December, one day before Christmas Eve, Helena Horton reported evidence from a study showing that black grass – a native annual weed – is developing resistance to glyphosate in the field. Glyphosate is currently approved for use as a herbicide in the EU until 2022 but is banned or restricted in many countries listed here.
Nine months earlier the paper had been published in the New Phytologist, Evolutionary epidemiology predicts the emergence of glyphosate resistance in a major agricultural weed (March 19th) followed on June 20th by an interesting commentary on the study which said:
“Although resistance to herbicides initially did not appear to evolve as rapidly as did cases of insecticide resistance (Gressel & Segel, 1978), over 240 weeds are now resistant to a variety of herbicides following c.70 years of herbicide use (Heap, 2019).
“Currently, there are c.41 weed species that have evolved resistance to glyphosate (Heap, 2019). Strikingly, what we have learned about glyphosate resistance evolution from these species all stems from studying the weeds after they become problematic to the farmer. This means that we are most often considering glyphosate resistance evolution in a reactive, rather than proactive fashion”.
Farming UK reported on the research paper in June, quoting the lead author, Dr David Comont, a weed ecologist from Rothamsted Research, who said the work provides 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”
The Telegraph reported on the research published in New Phytologist, on an article in ZSL Science (Zoological Society of London) and referred to a study in the journal Nature.
It repeated ZSL’s warnings that the UK’s food security is being put at risk by herbicide-resistant black-grass and its call for a ban on overuse of weed killer: “Black grass out-competes wheat for soil nutrients and reduces the number of wheat plants where it grows – and it is likely to spread further across the UK. This would increase the prices of bread and biscuits, and there would be less animal feed available so could also affect how much meat costs”.
Worldwide, there are 253 herbicide-resistant weeds, so the global impact of further resistance could be enormous. Nature’s study recommends urgent national-scale planning to combat resistance and the provision of incentives for increasing yields through food-production systems rather than herbicides. Dr Varah, the lead author, added that farmers need to implement more truly integrated pest management strategies – including diverse crop rotations and strict field hygiene measures.
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