Indianapolis, Indiana
August 24, 2006
An outbreak of
western bean cutworm (WBCW) in parts of the Western Corn Belt,
particularly in Iowa and Nebraska, has caught many corn
producers by surprise, leaving them scrambling to make rescue
insecticide applications and re-considering their in-plant trait
selection for the 2007 production season.
“Many growers
are finding worm levels above economic thresholds for the first
time since western bean cutworm moved into Iowa several years
ago,” says John Long, District Agronomist for
Mycogen Seeds. “If corn
producers haven’t scouted their fields, yet, they need to get
out there immediately. If they’ve found that the worms have
reached the silks and are feeding on ears, it may be too late
and very difficult to control them with an insecticide at that
point.”
Long adds that
corn producers who planted hybrids containing the Herculex® I or
Herculex® XTRA Insect Protection in-plant trait have
protection against WBCW. However, those hybrids containing the
YieldGard® in-plant trait do not offer protection against WBCW.
“There are a
lot of corn producers who were considering the impact that
western bean cutworm might have on corn this year, but chose
YieldGard as a result of recommendations they received or a
belief that western bean cutworm would not impact them this
year,” Long says. “Needless to say, they are wishing they had
selected Herculex I or Herculex XTRA.”
As of August
4, 63 of the 80 counties in Iowa where moths are being monitored
have seen moth captures at levels of greater than 100 per week.
Of those, 38 have seen moth captures of greater than 500 per
week. (Visit
www.ent.iastate.edu/trap/westernbeancutworm/image/tid/406 to
see the latest moth trap counts throughout the Midwest.)
In addition,
seven counties in northwestern Illinois and one in northwestern
Indiana have moth captures of greater than 100 per week. WBCW
moths have been trapped as far east as northwestern Ohio, which
suggests that WBCW is rapidly moving eastward from its origins
in western Nebraska and has grown to a pest of importance to
Corn Belt producers.
“It’s safe to
say that western bean cutworm is here to stay in the Corn Belt,”
Long says. “I also think it would be wrong to characterize it as
just a nuisance pest. It certainly has an attitude bent toward
hurting yields and profitability. We need to be aware of its
movement.”
Scouting
and Rescue Sprays
Maynard Ochs, product development agronomist for
Dow AgroSciences, says that as growers move into fields to scout
for WBCW that they need to be aware that corn holds a much lower
threshold to WBCW than what growers are accustomed to when
evaluating European corn borer (ECB) infestations. While
thresholds for ECB run at levels of 25 percent to 50 percent,
thresholds for WBCW are 8 percent for field corn and 5 percent
for popcorn or sweet corn. With many pests, one larva per plant
rarely causes economic injury.
“It takes a
high percentage of infested plants to do serious damage.
However, studies show that just one western bean cutworm larva
per plant can reduce yield by 3.7 bushels per acre. In severe
infestations, multiple larvae per ear may be common, as western
bean cutworm is not cannibalistic like corn earworm. Under heavy
feeding pressure, 50 percent to 60 percent of an ear’s kernels
may be damaged, resulting in serious losses,” Ochs explains.
The timing of an insecticide treatment to control
WCBW is also key. “It’s important to make rescue sprays before
the larvae reach silks. Otherwise, they find protection from the
insecticide under the husks,” Ochs says.
So long as the worms have not found cover within
the silk and under the husks, they may be controlled with an
insecticide like Lorsban®-4E insecticide or any number of
available pyrethroid insecticides, Ochs adds.
“Typically, you want to be scouting for egg
masses on the upper side of the upper leaves beginning in
mid-July when peak moth flights occur to determine if you have
economic threshold levels of western bean cutworm,” Ochs says.
“If eggs have hatched, insecticide applications can begin once
95 percent of the plant tassels have emerged, but before the
larvae move to the silks.”
There are numerous university sites available to
learn more about scouting and treating for WBCW, including:
§
Nebraska (www.ianrpubs.unl.edu/epublic/live/g1359/build/g1359.pdf)
§
Iowa State (www.ipm.iastate.edu/ipm/icm/2006/7-10/wbc.html)
§
Illinois (www.ipm.uiuc.edu/bulletin/article.php?id=598)
§
Purdue
(news.uns.purdue.edu/html3month/2006/060804.Krupke.cutworm.html)
Traits,
Seeds Considerations for 2007
As a result of
WBCW becoming a pest of economic importance, Ochs says that corn
producers seeking protection against WBCW need to consider the
following as they make their seed and in-plant trait decision
for 2007:
-
If they
want protection from an in-plant trait, they need to go with
hybrids containing either Herculex® I or Herculex XTRA
Insect Protection. The YieldGard in-plant traits do not
provide activity against WBCW, while Herculex will provide
very good protection against WBCW.
-
Corn
rootworm (CRW) is a determining factor in which Herculex
trait to select. Herculex I controls above-ground pests,
including WBCW, ECB, black cutworm, fall armyworm,
southwestern corn borer and corn earworm. If corn producers
also need control of CRW, Herculex® XTRA Insect
Protection is their choice because it contains both
Herculex I and Herculex RW Rootworm Protection, which
offers control of CRW.
“The way I
look at it is, if you are a corn grower and you are uncertain
whether western bean cutworm will be a problem pest for you in
2007, your simplest approach is to purchase a
hybrid with
either the Herculex I or Herculex XTRA in-plant trait,” Ochs
says. “You’re essentially buying peace of mind that you won’t
need to be out there scouting next summer like you would if you
use the YieldGard trait.
“Otherwise,
you can go the route of keeping an insecticide treatment in your
back pocket.
You just need
to be certain you will be proactive about scouting for the egg
masses and not procrastinating to the point you miss the window
of opportunity to control those larvae with an insecticide
treatment.”
Available
Hybrids for 2007
Long says that
Mycogen Seeds will offer 58 new grain corn hybrids next year,
including several stacked-trait hybrids containing Herculex®
XTRA Insect Protection, Roundup Ready® and LibertyLink
technologies. The majority of hybrids from Mycogen Seeds contain
Herculex I Insect Protection.
“These new
grain corn hybrids feature elite genetics, so growers get
top-performing hybrids, excellent standability and ultimately
higher yields,” Long adds.
Since European
Union (EU) import approval is pending, Herculex RW Rootworm
Protection and Herculex XTRA are Market Choices® products.
Grain containing either product must be marketed domestically,
fed on-farm, or delivered to elevators or other markets where
neither the grain nor its processed products (e.g., gluten) will
be shipped to the EU.
Grain from hybrids containing Herculex I only is
fully approved for food and feed use in the European Union;
however, this approval does not apply to grain (or processed
products from this grain, e.g. gluten) from Herculex® I
Insect Protection hybrids stacked with Roundup Ready® Corn
2. Grain from hybrids containing Herculex I and Roundup Ready
corn is a Market Choices product and must be marketed
accordingly.
Mycogen Seeds is a retail seed company of Dow
AgroSciences LLC and a developer and marketer of leading grain
corn hybrids, the market leader in Silage-Specific™ corn hybrids
and sunflower hybrids, as well as an industry leader in canola,
alfalfa, soybeans and sorghum. For more information on Mycogen
brand products, visit
www.mycogen.com.
Dow AgroSciences LLC, based in
Indianapolis, Indiana, USA, is a top-tier agricultural company
providing innovative crop protection, seeds and biotechnology
solutions to serve the world’s growing population. A wholly
owned subsidiary of The Dow Chemical Company, global sales for
Dow AgroSciences are $3.4 billion.
®™Mycogen,
the Mycogen Logo and Silage-Specific are trademarks of Mycogen
Corporation.
®Herculex is a trademark of Dow AgroSciences LLC
®Roundup Ready is a registered trademark of Monsanto Company.
®LibertyLink are registered trademarks of Bayer CropScience.
®Market Choices is a certification mark used under license from
ASTA.
©2006 Mycogen Seeds. Mycogen Seeds is an affiliate of Dow
AgroSciences LLC.
Herculex Insect Protection technology by Dow AgroSciences and
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