Roundup Ready Soybeans Giving Rise to Superweeds
The Kansas City Star
August 29, 2001

Weeds developing resistance to widely used herbicide, some say
By Scott Canon

COLUMBIA, Mo. _ Water hemp disappoints.
As weeds go, it looks so ... common.
Broad but not huge leaves. A stalk that runs from pure green to half
crimson, but never eye-catching.
Could this scrawny member of the pig weed family have stumbled upon the
herbicide-resisting powers that agri-giant Monsanto implanted in crops only
after years of laboratory gene tinkering? Is this, the humble amaranthus
tuberculatus, a superweed?

"Right now, I'm just calling it insensitive," said Reid Smeda, a University
of Missouri-Columbia weed scientist.
He's studying whether a strain of water hemp _ no relation to the stuff used
for rope or dope _ plucked from northeast Missouri and west-central Illinois
can shrug off the popular herbicide glyphosate.

Weeds overcome herbicides all the time. But glyphosate, best-known as
Monsanto's Roundup brand, kills virtually everything green.
That's why genes were custom-fitted into crops specifically to withstand the
weed killer king. With such seeds, a farmer can plant a genetically modified
crop, spray with glyphosate and expect all the pest plants to whither while
grain grows unharmed.

Farmers, in fact, love the simplicity of it all.
Such trademarked Roundup Ready varieties account for four out of every five
American acres planted with soybeans. Roundup Ready corn, canola and cotton
have been popular as well. Monsanto soon could offer herbicide resistance in
sugar beet, rice, wheat and lettuce. Already, the technology is locked
solidly into the nation's food chain.
Water hemp could ruin all the fun.

It could, in fact, fulfill the prophecy of environmentalists that widespread
use of herbicide-resistant crops eventually will lead to the rise of
herbicide-resistant weeds _ breeds of super weeds.
"Given enough generations and enough exposure, any species will develop
resistance to a herbicide," said Rebecca Goldburg, a senior scientist for
anti-biotechnology Environmental Defense.

Monsanto is more than skeptical. David Heering, the company's lead expert,
disagrees with the theory that continued use of Roundup Ready crops
inevitably will lead to superweeds.
"I would challenge anybody," he said, "who says they're going to predict
weed resistance to herbicides."

So far, water hemp has given only an inkling of Roundup resistance. Native
to the Grain Belt, it is the most common weed in Missouri soybean fields and
is on the way to being the most common weed in the state's corn fields.
Its genetic background is highly diverse _ "It's the U.N. of plants," Smeda
said _ and that increases its chances of coming up with a strain that will
resist what farmers throw at it.

In 1999, a farmer near Monticello, Mo., and another near Sutter, Ill.,
reported that some water hemp was shocking them by surviving glyphosate,
albeit at low rates.

Both locations were Roundup Ready soybean fields treated season after season
with glyphosate.

At first skeptical, Smeda collected samples for dousing in herbicide at his
University of Missouri-Columbia greenhouse along with tests in the field.
In both settings, he found that some water hemp plants survived sprayings of
glyphosate _ sold as Roundup, Touchdown, Glyphomax, Glyphos _ at higher
rates than other weeds.

In greenhouse conditions, 4 percent to 5 percent of the suspect water hemp
plants survive sprayings with glyphosate, almost regardless of the dosage.
"Under those conditions, you'd expect a 100 percent kill," Smeda said.
He's puzzled, however, because the offspring of those survivors demonstrate
the same 5 percent survival rate, when science might predict them to inherit
their parents' sturdier character.

Smeda thinks farmers will need to rotate their herbicides, which would mean
planting something other than Roundup Ready crops.
"The Roundup Ready technology is so good, we don't want to lose it," Smeda
said.

In Delaware, weed scientist Mark VanGessel has a horseweed, commonly known
as mare's tail and categorized scientifically as conyza canadensis, that
appears to have whipped glyphosate.

When he first got reports from around the state of resistance in 1999,
VanGessel admits he was dismissive.

Dousing samples with glyphosate, he found to his own surprise that "it
stunts them, but it won't kill them."

"Farmers had been using Roundup for 25 years, and there was no resistance
yet," said VanGessel. "It turns out the operative word was 'yet."'
But those decades before Roundup Ready was introduced five years ago were
different. Glyphosate was used in rotation with other weed killers,
depending on the weed problem, and the timing of planting cycles. With new
gene-spliced designer Roundup Ready soybeans, however, there seemed little
reason not to use glyphosate exclusively.

The problem, say agronomists, is that continually killing off the herbicide
weaklings leaves less competition -- for nutrients in the soil, for water,
for light _ for that random genetic mutation that can weather a rain of
Roundup.

"This is kind of a wake-up call that we can't rely on glyphosate year in and
year out for weed control," VanGessel said.

Monsanto greets such reports with skepticism. The company's patent on
glyphosate expired Sept. 20, 2000. But it continues to sell the herbicide
and license the sale of Roundup Ready seed.

Roundup is much more environmentally friendly than other popular herbicides.
Atrazine, for instance, can pose a problem for soil and water pollution
years after it is first applied. Evidence of glyphosate use, in contrast,
can disappear in a matter of days.

Heering, Monsanto's expert, concedes that goose grass in Malaysia and rye
grass in Australia have shown resistance to glyphosate. But that has nothing
to do with Roundup Ready crops. There, glyphosate is used like other
traditional weed killers, without any coordination with genetically altered
seeds.

Even there, he said, the company is making recommendations about mixing
Roundup with other varieties.

As for the mare's tail and water hemp, Heering is not ready to concede. The
company reads the data on water hemp to detect no resistance and is awaiting
some tests of the mare's tail.

The consensus among weed experts holds that if water hemp hasn't developed
resistance to Roundup, some other American weed eventually will. Mare's
tail, insists VanGessel and others, already has. Farmers then will be forced
back to changing their herbicide from one year after the next or risk fields
choked with superweeds.

"The simplicity of the Roundup Ready system is not going to last very long,"
said Dale Shaner, a co-author of Herbicide Resistance and World Grains.
"Most simple systems just don't stand up. Mother nature has a way to get
around that."

Still others concede that if Roundup is destined for a showdown with
superweeds, it holds a considerable edge now.

"There's a lot of (Roundup) being used," said Michael Christoffers, a weed
geneticist at North Dakota State University. "If it were easy for weeds to
develop resistance to it, we'd be seeing that happen much more often."

(c) 2001, The Kansas City Star.
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