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9-Misc: Monsanto confirms case of glyphosate-resistant Palmer Pigweed



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TITLE:  Investigation Confirms Case Of Glyphosate-Resistant Palmer Pigweed
        In Georgia
SOURCE: Monsanto, USA
        http://www.monsanto.com/monsanto/layout/media/05/09-13-05.asp
DATE:   13 Sep 2005

------------------ archive:  http://www.genet-info.org/ ------------------


Investigation Confirms Case Of Glyphosate-Resistant Palmer Pigweed In Georgia

ST. LOUIS (Sept. 13, 2005) - Dr. Stanley Culpepper, a University of
Georgia weed scientist, and Monsanto have determined that Palmer amaranth
(Palmer pigweed) at specific sites in central Georgia is resistant to
glyphosate, the active ingredient in Monsanto's Roundup(R) agricultural
herbicides. Numerous field and greenhouse trials completed earlier this
year indicated probable resistance; however, heritability studies -- to
determine whether the lack of control is passed on to the next generation
-- are now complete and confirm this Palmer amaranth population as resistant.

"This Palmer amaranth population has tolerated extremely high rates of
glyphosate applied in the field under excellent growing conditions," says
Culpepper. The resistant population infests 500 acres of Roundup Ready(R)
cotton in central Georgia. Additional herbicide products have provided
effective control of the resistant population. Dr. Culpepper and Monsanto
are surveying the surrounding area this season to determine if this
biotype has spread.

When glyphosate resistant weed biotypes have been identified in the past,
they have been effectively managed with other herbicides and/or cultural
practices, such as tillage. Based on the data available today, Monsanto
recommends that farmers growing Roundup Ready cotton or Roundup Ready
Flex(R) cotton who have glyphosate-resistant Palmer amaranth on their
farm do the following for 2006:
- Use a pre-emergence residual herbicide such as Prowl(R)
- Apply Roundup agricultural herbicide plus metolachlor early post-emergence
- Apply Roundup agricultural herbicide plus diuron at lay-by

In case of weed escapes, there are other herbicide products available as
well. Growers should always read and follow herbicide label directions.
Monsanto will continue to work with the University of Georgia to research
the best options for control of glyphosate resistant Palmer amaranth and
will modify these recommendations as new information becomes available.

"We have ongoing research planned to investigate Palmer amaranth
management systems for a number of crops," says Culpepper. "We won't be
sure what the best recommendation is until after the cotton harvest."

For growers that do not have confirmed glyphosate-resistant Palmer
amaranth, Monsanto is recommending they use a pre-emergence residual that
is active on Palmer amaranth, such as Prowl, in addition to a Roundup
agricultural herbicide.

"Using a residual helps reduce early season weed competition and reduces
the number and size of weeds when the first application of Roundup is
made," says David Heering, Roundup Technical Manager. "In cotton, it is
also important to add a residual at lay-by such as diuron to control
weeds that emerge between lay-by and harvest."

Growers who are planting other Roundup Ready crops, such as corn or
soybeans, should also use a pre-emergence residual if they have Palmer
amaranth in their fields. Additionally, using the right rate of
glyphosate for the right size weed at the right time is critical in an
effective weed control program. The use of lower than recommended rates
of glyphosate has been a contributing factor in previous cases of
confirmed glyphosate resistant weeds. Growers should also consider using
additional weed control tools that may be necessary for the weed spectrum
on their farm.

The research on Palmer amaranth will be submitted to the International
Survey of Herbicide Resistant Weeds at www.weedscience.com. for inclusion
on the official list of glyphosate-resistant weeds.

Monsanto Company is a leading global provider of technology-based
solutions and agricultural products that improve farm productivity and
food quality. For more information on Monsanto, see: www.monsanto.com




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