http://story.news.yahoo.com/news?tmpl=story2&u=/ap/20030913/ap_on_sc/superweeds&e=2
Sat, Sep 13, 2003
Weeds Seen More Resistant to Herbicide
By EMILY GERSEMA, Associated Press Writer
WASHINGTON - Increased
findings that weeds are developing resistance
to Roundup, the world's most popular herbicide, have some scientists
urging new planting practices. The product's manufacturer says
the
problem is being overblown.
Roundup, whose generic
name is glyphosate, has been on the market
for more than 30 years. It long has been a favorite of farmers,
home gardeners and golf course greenskeepers because of its
effectiveness in killing weeds.
It allows growers to
cut back on tilling, a more labor-intensive
and expensive method of controlling weeds, and does not pollute
the environment.
"Roundup Ready"
crops, which have been genetically altered
to tolerate the chemical, now cover much of the nation's farmland
since their development in the late 1990s. They allow farmers
to spray the glyphosate herbicides widely without harming crops.
The Agriculture Department
estimates that 80 percent of the
73 million acres of soybeans in the United States are Roundup
Ready soybeans, and Roundup Ready cotton accounts for more
than 30 percent of the 12 million acres planted. The corn
variety, still new to the market, covers 11 percent of
70 million acres.
"Farmers are planting
too many Roundup Ready crops,"
said Stephen Powles, an expert on weed resistance at
the University of Western Australia.
The herbicide is vital
for food production systems in the
United States and in many other parts of the world, Powles
said. Should weed resistance become widespread, he said,
"I think the problem will become a crisis."
In 1996, Australia
was the first to note that weed resistance
to glyphosate was developing in rigid ryegrass found in a
few grain and sorghum fields. Five years later, South Africa
reported seeing the resilient rigid ryegrass had infested
a few hundred acres of vineyards.
In 2000, University
of Delaware scientists reported to the
Weed Science Society of America, which tracks farm chemical
resistance, that in some soybean fields, mare's tail was
resisting glyphosate. Since then, resistant mare's tail
has been reported in other states - Indiana, Kentucky,
Maryland, New Jersey, Ohio, Arkansas, Mississippi and
Tennessee.
Far more worrisome
are cases in Iowa, Illinois and Missouri,
where glyphosate is becoming ineffective on abundant weeds
such as velvet leaf and water hemp.
Allan Felsot, an environmental
toxicologist at Washington State
University, said weeds naturally develop resistance to a pesticide
and dismissed the idea they might be picking up a resistant gene
from Roundup Ready soybeans, corn or cotton.
"Any time you
have a place where you're using a strictly singular
herbicide, you may end up with some resistance in some cases,"
he said.
Nonetheless, some scientists
want farmers to alter their planting
practices to assure that Roundup and competing brand names of
glyphosate maintain their effectiveness as a herbicide in the
future. The Australian Powles advocates cutting back on plantings
of Roundup Ready crops.
Mark VanGessel, a weed
scientist at the University of Delaware,
advocates a more moderate course. He suggested that farmers rotate
their Roundup Ready crops with conventional varieties.
"My gut reaction
is that we do need to limit the use of
glyphosate-resistant crops," VanGessel said. "That doesn't
necessarily mean don't develop them or don't use them
altogether, but instead use a planned approach so to not
use the glyphosate-resistant crops year in and year out."
Monsanto Co., which
markets Roundup Ready crops in addition
to the herbicide, said the problem is not nearly that severe.
"Most of the situations
that we're dealing with, we're dealing
with very small acres," said Greg Elmore, a soybean technical
manager at Monsanto. "We're not talking about a whole county.
In some cases, we have one field only."
Regardless, farmers
could turn to tilling and a combination
of other chemicals besides glyphosate, he said.
Monsanto's competitor,
Syngenta, agrees with VanGessel that
farmers should rotate planting of Roundup Ready corn and soybeans
with conventional crops. Syngenta makes its own glyphosate spray,
Touchdown.
"We really feel
like the problem is real and the problem is growing,"
said Sherry Ford, a Syngenta spokeswoman. "Just like with
antibiotics,
an overreliance on one type of solution is going to eventually
make
that solution ineffective."
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On the Net:
Weed Resistance: http://www.farmassist.com/resistance/
Weed Survey: http://www.weedscience.org/in.asp
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