Memphis, Tennessee
March 12, 2008
- University of Arkansas partners
with Monsanto in Crittenden, AR case
- Company leads investigation in Mississippi Delta
The University of Arkansas and
Monsanto have confirmed
glyphosate resistant johnsongrass in a field in southeast
Arkansas. In a separate case, Monsanto and specialists at
Mississippi State University confirm a case of johnsongrass
resistance to glyphosate near Clarksdale, Mississippi.
The two cases were investigated over the past several months. In
initial greenhouse trials conducted by the University of
Arkansas and Monsanto, johnsongrass was not controlled with
labeled rates of glyphosate. Additional trials will be conducted
in the field this season.
“We’re looking at johnsongrass populations in a field where
there has been a history of control issues,” says Dr. Bob Scott,
University of Arkansas Extension Weed Scientist. The field in
question is owned by a grower near Crittenden County, Arkansas,
and has been in continuous Roundup Ready soybeans.
“Our greenhouse trials show differing levels of response
including some plants that survive following application above
labeled rates of glyphosate. Additional populations suspected to
be resistant, were also tested but shown susceptible to Roundup
in testing,” says Scott. “The resistant populations are being
controlled well with selective chemistry. We will continue
working with the grower on control methods and recommendations.”
Monsanto’s technology development team has been working with a
farmer and his dealer outside of Clarksdale, Mississippi on a
field with johnsongrass control issues as well. Dr. Trey Koger
and Dr. Dan Poston of MSU’s Delta Research & Extension Center
are working with the company on recommendations.
“The farm where glyphosate resistant johnsongrass was found in
the Delta has responded well to applications of graminicides,”
Koger explains. “We are working with the grower to get control
of this population before it spreads by combining various
methods including chemistry and equipment inspection.”
Like Scott, Koger says other populations have been screened as
well. “We have screened several populations of johnsongrass in
the mid-Delta for potential resistance to glyphosate. They all
turned out to be susceptible to glyphosate in greenhouse trials.
We determined low control levels in the field were attributed to
extremely dry conditions at time of glyphosate application.”
Dr. Jennifer Ralston, US Chemistry Technical Lead for Monsanto
agrees a program approach is best. “We are working with these
university experts to provide growers with the best management
practices. To maintain the efficacy of the herbicide and value
of the technology, we recommend growers scout fields and utilize
additional modes of action that complement the Roundup Ready
system to control problem weeds while reducing the likelihood of
developing performance issues.”
The company and academics recommend growers adopt best
management practices to help growers minimize the risk of
developing resistant weeds practices including:
- Start with a clean field
by either utilizing a burndown herbicide or tillage to
control weeds early.
- Use Roundup Ready
technology as the foundation of a total weed management
program.
- Add other herbicides or
cultural practices where appropriate as part of the Roundup
Ready cropping system.
- Use the right herbicide
rate at the right time.
- Control weeds throughout
the season and reduce the weed seed bank.
Monsanto Company is a leading
global provider of technology-based solutions and agricultural
products that improve farm productivity and food quality.
Roundup and Roundup Ready are registered trademarks of Monsanto
Company.
Other news
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