A widely used herbicide encourages the growth of toxic fungi that devastate wheat fields, laboratory studies by scientists working for the Canadian government suggest.
If field studies confirm that the herbicide, glyphosate, increases the risk of fungal infections – which are already a huge problem – farmers might be advised to use it less.
That could be a major blow for backers of genetically modified wheat in Canada, because the first GM variety up for approval in Canada is modified to be glyphosate-resistant. If it gets the go-ahead, there is likely to be an overall increase in glyphosate use.
The potential problem was spotted a few years ago by Myriam Fernandez of the Semiarid Prairie Agricultural Research Centre run by Agriculture and Agri-Food Canada in Swift Current, Saskatchewan. She noticed that in some fields where glyphosate had been applied the previous year, wheat appeared to be worse affected by fusarium head blight – a devastating fungal disease that damages grain and turns it pink.
In Europe alone, fusarium head blight destroys a fifth of wheat harvests. The fungi that cause the disease also produce toxins that can kill humans and animals.
In a follow-up study, Fernandez measured levels of the blight in wheat fields. “We found higher levels of blight within each tillage category when glyphosate had been used in the previous year,” says her colleague Keith Hanson.
And his lab study showed that Fusarium graminearum and F. avenaceum, the fungi that cause head blight, grow faster when glyphosate-based weedkillers are added to the nutrient medium.
But the investigators warn against jumping to conclusions. “We’re deferring judgement until we have all the data,” says Hanson. His team is now planning field and greenhouse trials.