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Watching for Resistant Weeds
By
Laura Skillman
PRINCETON, Ky., (Jan. 3, 2007) – So far, Kentucky has only a few
weeds that have developed resistance to chemicals used to
control them, but vigilance and proper use is essential to
ensure that control measures will continue to be effective.
There are seven weedy biotypes that have been confirmed to be
resistant to at least one chemical control in Kentucky. Other
control measures are still available to combat these pesky
weeds.
“Kentucky farmers have done a pretty good job, but we are
slipping. We’ve got to be on our toes,” said Jim Martin, weeds
specialist with the University of Kentucky College of
Agriculture. “I have to believe that the reason we don’t have
the problems of some of our neighboring states is the cropping
rotation that we are using – corn, wheat and soybeans. That
rotation to some extent has helped to minimize our resistance.
Generally, where we see those problems is where we don’t see
this kind of a rotation.”
Farmers are moving away from the traditional crop rotations
somewhat because of strong prices for corn, so other options
will be needed to control weeds.
Heavy reliance on the same chemistry can result in shifts in
weed populations that are resistant to the product. That doesn’t
mean abandoning a product that has long proven successful,
Martin said. It does mean respecting the product, using it in
the appropriate rates and not using it as the sole source of
control year after year.
Finding the right mix of products that can ensure proper weed
control is an important tool in keeping as many products
available as possible to combat weeds.
In Kentucky the majority of soybeans produced are “Roundup
ReadyŠ,” meaning they are resistant to the herbicide glyphosate,
allowing the chemical for weed control while not damaging the
beans.
Using a residual herbicide prior to planting can be helpful in
minimizing the weed competition, especially for corn early in
the growing season, he said. It also buys more time before the
corn will need to be sprayed with glyphosate to maintain the
weed control.
In 2006 volunteer corn was a problem in many soybean fields and
will likely be a problem in 2007, especially if it is in a field
where Roundup ReadyŠ corn is being followed by
Roundup ReadyŠ soybeans, he said. Using glyphosate on the crop
will not kill the corn and another herbicide will have to be
used to kill it. There are options to control volunteer corn in
Roundup ReadyŠ soybeans if glyphosate cannot be used.
Controlling volunteer corn is important because of the
detrimental impact it can have on soybean yields.
“The sooner it can be treated the better, generally within two
to four weeks after emergence,” he said. |
Contact: Jim Martin, 270-365-7541, ext. 203 |
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The UK College
of Agriculture, through its land-grant mission, reaches across
the commonwealth with teaching, research and extension
to enhance the lives of Kentuckians. |
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