Karma.
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Sent: 10/1/2013 2:25:37 P.M. Central Daylight Time
Subj: GMW: Disease lays waste to GM corn in the US
The unravelling of GM agriculture continues in the US, as a devastating
disease, Goss's wilt, lays waste to GM corn.
Monocultures of GM corn all developed from varieties with low resistance
to the disease are primarily blamed. The no-till farming practiced with GM
herbicide-tolerant crops is also named as a possible culprit, since corn
debris left on the soil can harbour disease.
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A disease cuts corn yields
STEPHANIE STROM
New York Times, September 30, 2013
http://www.nytimes.com/2013/10/01/science/earth/a-disease-cuts-corn-yields.h
tml?_r=1&
It has come on like a tidal wave, washing across the Corn Belt from
Minnesota to the Texas panhandle, a disease that few farmers had seen until five
years ago.
Known as Goss’s wilt, it has cut some farmers’ corn yields in half, and
it is still spreading. This summer it reached Louisiana, farther south than
it had ever been identified. Alison Robertson, a plant pathologist at Iowa
State University, estimated that about 10 percent of this year’s corn crop
would fall to Goss’s.
The disease, named for R. W. Goss, a longtime Nebraska plant pathologist,
is caused by a bacterium with the formidable name Clavibacter michiganensis
subsp. nebraskensis. When a plant is damaged by hail or other heavy
weather, the microbe enters the wound and infects its vascular system, scarring
the leaves with brownish-yellow lesions sprinkled with black freckles.
The infection may or may not kill the plant, depending on when it comes,
but it almost always curtails yields. And for farmers who have never seen
the infection before, it is deeply disconcerting.
“The farmer who called me had found a circle of corn about 50 feet in
diameter or so that had strange symptoms, stalks broken over and twisting,
discoloration, the whole nine yards,” said Clayton Hollier, a plant pathologist
at Louisiana State University. “I hadn’t heard symptoms like that since I
learned about Goss’s in college.”
Until 2008, Goss’s wilt had been confined to western Nebraska and a
handful of counties in eastern Colorado. But that year it was found in Iowa,
Illinois, Indiana and Wisconsin.
In 2011, a particularly virulent year, farms in much of Illinois lost as
many as 60 bushels of corn per acre to the disease (the usual yield is 200
bushels per acre). So did many counties in Indiana.
While there are no official tallies, the last two years do not appear to
have been as bad — thanks in part to dry, hot weather, which tends to keep
the disease at bay. But its continuing spread is worrying farmers and plant
pathologists throughout the Corn Belt.
No one is certain why Goss’s wilt has become so rampant in recent years.
But many plant pathologists suspect that the biggest factor is the hybrids
chosen for genetic modification by major seed companies like Monsanto,
DuPont and Syngenta.
“My theory is that there were a couple of hybrids planted that were
selected because they had extremely high yield potentials,” said Dr. Robertson,
whose research is financed by Monsanto and the Agriculture Department. “They
also may have been highly susceptible to Goss’s wilt.”
About 90 percent of the corn grown in the United States comes from seeds
that have been engineered in a laboratory, their DNA modified with genetic
material not naturally found in corn species. Almost all American corn, for
instance, is now engineered to resist the powerful herbicide glyphosate
(often sold as Roundup), so farmers can kill weeds without killing their corn.
Farmers often refer to such biotech plants, which require Agriculture
Department approval, as “traited,” to distinguish them from traditional
hybrids.
While some corn seeds are resistant to Goss’s wilt, especially those sold
in western Nebraska and eastern Colorado, most are not. Dan Anderson,
Monsanto’s lead project manager for corn, acknowledged that high-yield varieties
from his and other companies might be susceptible to the disease, but
added that changes in farm management might also be spreading the disease. As
farmers grow more corn to satisfy the demand for ethanol, they are rotating
it less frequently with other crops.
“One of the best management techniques for controlling Goss’s wilt is
crop rotation — corn, then soy or another crop,” Mr. Anderson said.
Another possible factor is the growth of no-till farming, which leaves
cornstalks, on which the bacteria can linger, to decay in the field after
harvesting, rather than being plowed under.
No hybrids have been developed that can fully withstand Goss’s wilt, but
the companies have increased the number of seeds with higher resistance.
Ryan Forth and his father farm about 4,500 acres of land north of Ames,
Iowa, about two-thirds of it in corn and the rest in soybeans. Mr. Forth is
also a seed dealer for Monsanto. Some seeds in the company’s DeKalb line
have been identified as highly susceptible to Goss’s.
After a windstorm in 2010, he said, “we started seeing these weird little
circles on the foliage” in the field where the DeKalb seeds were planted.
At first they thought the marks were because of wind damage or the lack of
rain — “you always suspect the weather,” he said — but now he’s certain
it was the choice of hybrid that caused the problem.
The next year, they planted the same hybrids. “We were the poster child
for Goss’s that year,” Mr. Forth said. “We had a complete disaster, a
train-wreck kind of a yield for me.”
Last year, he planted a different Monsanto hybrid and has not had a
problem with Goss’s wilt since. He no longer sells the DeKalb hybrids that
contract the disease.
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