-------- Original Message --------
From: "Mark Graffis"
Subject: Herbicide `Roundup' may boost toxic fungi

New ScientistWeedkiller may boost toxic fungi

12:16 14 August 03

Exclusive from New Scientist Print Edition.
http://www.newscientist.com/news/news.jsp?id=ns99994051

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.

Deadly toxins

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.

Dead plant matter

Hanson stresses that the real issue is whether the fungi leave more spores
in the soil. It is also possible that the effect is simply due to herbicides
leaving more dead plant matter in the soil for fungi to grow on and is not
directly caused by glyphosate. His field studies should provide answers next
spring, he says.
Monsanto, the company based in St Louis, Missouri, that sells glyphosate as
Roundup, as well as a number of "Roundup Ready" crops modified to be
resistant to it, claims that glyphosate is already widely used without
causing any apparent problems with fungi. Monsanto applied to the Canadian
government in December 2002 for approval of its Roundup Ready GM wheat. It
says it will be keeping a close watch on Hanson's research.
The team's initial findings are likely to be seized upon by anti-GM
activists. But switching to other herbicides could be bad news for the
environment - glyphosate is one of the least harmful herbicides, as it
quickly breaks down in the soil.
Ironically, Syngenta, another biotech giant, based in Basle, Switzerland,
has been developing and testing both GM and conventional wheat strains that
are resistant to the fusarium head fungi. "The results have been promising,"
says a Syngenta spokesman.

Andy Coghlan