Columbus, Ohio
May 17, 2007
The increased planting of Round-Up
Ready corn and other transgenics that are glyphosate-resistant
is creating challenges for growers who need to kill a failed
corn stand before replanting.
“Killing a failed corn stand for the purposes of replanting corn
used to be pretty straightforward. Apply glyphosate to the
failed corn, and plant the new corn stand. Or, plant the new
corn stand and then apply glyphosate to the failed stand before
the new corn emerges,” said Mark Loux, an
Ohio State University Extension
weed specialist. “However, killing the failed stand has become
somewhat more complicated in fields where Round-Up Ready corn
was planted initially.”
When using glyphosate is not an option, the alternatives can get
complicated, and in some cases, more expensive. Time is also
working against the grower when it comes to replanting.
“A grower can get his corn in by April 15 and then realize on
May 10 that his stands failed,” said Loux. “He has to get that
second stand going quickly. Every day counts with planting corn
when you run the risk of losing a bushel a day after the optimum
planting date.”
The following are several options for the control of Round-Up
Ready corn in replanting situations:
- The most effective
treatment is the use of Select Max. Loux said that it is
inexpensive (around $5 per acre), but at least a five-day
waiting period to plant corn is required after application
to avoid plant injury and problems in stand establishment.
“Ohio Department of Agriculture obtained a Section 18 Crisis
Exemption label for use of Select Max to control failed
stands of Round-Up Ready corn. That temporary label is valid
until May 24,” said Loux.
- A mixture of Gramoxone
Inteon and metribuzin is the best option when it is not
possible to wait five days to replant. “However, for reasons
we don’t know, metribuzin is in short supply this year, so
it may be difficult to secure that ingredient to make the
application effective,” said Loux. “This treatment is
effective in corn less than 5 inches tall.”
- Application of Gramoxone
Inteon alone, or an application of Liberty, can also be
effective. But according to Ohio State University research
and studies conducted at other land-grant universities,
treatment was less effective on corn higher than three
inches. “We were able to obtain near complete control of
corn treated at the 3-inch stage, but control was generally
less effective when treating 11-inch corn,” said Loux.
For additional information on
applicable treatments of failed corn stands, refer to the Ohio
State University Agronomic Crops Team Web site at
http://agcrops.osu.edu.
Planting conventional corn hybrids is becoming less of an option
for growers, especially as transgenics -- Bt corn, stacked
traits -- become more popular. According to the U.S. Department
of Agriculture, 13 percent of Ohio’s corn planted last year was
herbicide-resistant. It is estimated that nearly half of Ohio’s
corn acreage will be planted with Round-Up Ready corn this year.
Transgenics is the science of introducing a gene from one
organism or plant into the genome of another organism or plant.
In crop production, Bt corn to control European corn borer and
rootworm, and Round-Up Ready corn and soybeans for enhanced weed
control would be examples of transgenics.
“Round-Up Ready soybeans helped to increase the popularity of
Round-Up Ready corn,” said Loux. “Round-Up Ready corn has now
become a big part of a seed company’s offerings. I wouldn’t be
surprised to see 80 percent to 90 percent of our corn acreage
Round-Up Ready in the next few years.”
The convenience of seed packages, low cost and higher yields
compared to conventional hybrids are also sparking an interest
in the use of Round-Up Ready corn.
Loux said increasing use of Round-Up Ready corn will create
challenges for growers when managing glyphosate, but ongoing
research on new herbicides and technology may offer additional
options in the future.
Corn is one of Ohio’s most valuable field crop commodities,
second to soybeans in acreage and economic value. According to
the Ohio Department of Agriculture, corn production contributes
$836 million to agriculture. |
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