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Looking for Soybean Stem
Borer
By
Laura Skillman
PRINCETON, Ky., (Aug. 8, 2007) – This fall soybean producers in
the state may be called upon to help scientists better
understand how widespread and damaging the soybean stem borer is
in Kentucky and several surrounding states.
The borer is not a new insect. Doug Johnson, entomologist with
the University of Kentucky College of Agriculture, has been
working for the past several years on what cultural practices
may help mitigate its impact. However, to date, planting date,
maturity group and variety have shown to be of little help. And
until recently, there was no insecticidal control.
The female borer will bite a section out of the node on a
soybean plant, put her egg in and then replace the section,
sealing the node. This protects the egg from insecticidal
sprays. Seed treatments or soil-applied insecticide also have
not worked.
Once the larva hatches and reaches a certain size it will tunnel
into the stem, ultimately reaching the bottom. With an
infestation, the physiological damage from the tunneling can go
up to about 10 percent damage, but if the beans fall over, the
damage and subsequent lost yields go even higher.
Two years ago a researcher in Kansas got 100 percent control
with a seed-applied insecticide that is labeled for use in corn,
not soybeans. Further testing on this insecticide is under way
at UK, Kansas State and Arkansas, in the hope that it can be
labeled for soybeans. This research includes two seed-applied
insecticides and two foliar-applied insecticides.
The university work is an effort to collect data needed to
convince the company to pursue the labeling requirements through
the U.S. Environmental Protection Agency.
“We probably will be able to collect the efficacy data,” Johnson
said. “But getting a pesticide labeled for a particular crop is
a very expensive thing to do, so the other data we will need is
a distribution of the insect and a calculation of how many acres
of soybeans are affected by this insect and to what extent.”
That’s where local soybean growers will play a role. Sometime
this fall, as a part of this project, Johnson will contact
soybean farmers and ask them if they have the insect, what
percentage of their fields might have it and what percentage of
plants in the field might have it.
“This is going to be very critical data, because we’ve got to
illustrate, providing the product works, that the company can
make enough money to go through the expensive labeling process.
We will have to come to soybean growers to gather this
information,” he said.
Johnson said it is important that they receive good farmer
participation to get the necessary information to present to the
insecticide company. But ultimately it will be the company’s
decision whether to pursue labeling the product.
“We continue to look at other options to mitigate the risk of
damage from the soybean stem borer such as earlier planting
dates, early maturing soybean groups and we might see some
differences, but they will probably be very small,” he said. “At
this time about the only thing a farmer can do is determine
whether they have them.”
The easiest way to do this is, when the beans are almost mature,
pull up a plant and split the stem. If borers have been active,
the stem will be completely hollowed out and sometimes packed
with frass. The plants can also snap off easily. It is not
uncommon to see the borer, as well.
To get a picture of how widespread and damaging the insect is,
farmers will need to check 20 to 30 plants in a field, then get
a percentage of those plants that are infested, a percentage of
their fields that are infested and the number of acres in the
fields. That’s the kind of information Johnson will collect in
coming months to document the need to the company and to the
EPA.
Johnson said they know the insect is in western Kentucky and at
least as far east as Lexington, but the eastern edge probably is
not very impacted by the insect.
Finding a means of combating the insect will stop the 10 percent
loss it inflicts on infested fields, he noted, as well as lessen
the likelihood that plants will fall and cause even higher
losses.
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Contact: Doug Johnson, 270-365-7541, ext. 214
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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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