Urbandale, Iowa
July 17, 2008
A soybean pest that has the
potential to rob soybean yield has again been sighted in Iowa.
The soybean aphid has been found across the northern half of the
state, and while the pests have not reached the level where
treatment is required, Iowa State University (ISU) Extension
entomologists and the Iowa
Soybean Association (ISA) urge soybean farmers to begin
scouting their fields.
“Soybean aphids are returning to soybean fields around the
state,” says Dr. Matt O’Neal, assistant professor of entomology
at Iowa State University. “Growers should scout now and into
August to determine if they will need to manage this pest with a
application of insecticide.”
The economic threshold for treating soybean aphids across the
Midwest is 250 aphids per plant and increasing. Despite the
significant increase in the value of soybeans, entomologists at
ISU and other universities are not altering their
recommendation. “We have no evidence that soybean aphid
populations below 250 per plant reduce yield,” added Dr. O’Neal.
“The density of this pest from year to year, and even from field
to field, is remarkably variable. By scouting and using the
threshold, growers can avoid an unnecessary application of
insecticide. Following this recommendation avoids killing
predators of the aphids that can keep populations down until
insecticide control is needed, if at all. In the long run, this
recommendation helps reduce the risk of aphids becoming
resistant to insecticides.”
Since the arrival of the soybean aphid to Iowa, significant
advances have been made in understanding this invasive insect’s
biology. The tools that are available to growers for managing
this pest have expanded as well. ISA and ISU are offering an
informational resource that will help soybean growers manage
this pest.
The pocket-sized Soybean Aphid Management Field Guide is a
portable, durable tool farmers can keep in the glove box of
their pickup truck and take to the field. This decision aid is
designed to answer questions about the specifics of managing
this potentially yield-robbing pest. The guide also includes
information on selection of insecticides and timing of
application, the use of seed treatments, and information on tank
mixing insecticides with fungicides and herbicides.
Also available to soybean producers is a companion publication
titled “Speed Scouting Soybean Aphids,” a new tool that offers
producers and crop professionals information on how to determine
whether or not they need to spray insecticides to control the
aphid population in their fields. Developed by scientists in
Minnesota, it helps soybean growers quickly and accurately
determine if the number aphids in a field have reached the
economic threshold.
“Speed Scouting Soybean Aphids is an excellent tool for soybean
producers who don’t like the idea of spraying indiscriminately.
Research has shown little or no yield loss when aphid
populations are below the economic threshold,” says Dr. David
Wright, ISA director of contract research. “The pocket-sized
Soybean Aphid Management Guide is a unique publication that
includes the most up-to-date information on soybean aphid
management. Both of these tools are designed to take the
uncertainty out of the decision of whether or not to spray for
soybean aphids.”
Either aphid publication is available by calling the Iowa
Soybean Association at (800) 383-1423. Also available is the
Soybean Disease and Pest Management Field Guide. This
publication is loaded with high quality images to help the user
easily identify yield-robbing soybean diseases and insects as
well as the latest soybean production information from Iowa
State University. The publications are offered at no cost by
Iowa State University through a partnership with the Iowa
Soybean Association and the soybean checkoff.
The Iowa Soybean Association develops policies and programs
that help farmers expand profit opportunities while promoting
environmentally sensitive production using the soybean checkoff
and other resources. The Association is governed by an elected
volunteer board of 21 farmers. |
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