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Where Will Aphids
Strike This Year?
Knowing where soybeans aphids will attack this year may
involve a case of history repeating itself, as was seen in many areas
last year. If that’s the case, growers should take precautions to
manage the bugs now to prevent major problems from mid-summer on.
As this newsletter has pointed out before, aphids may be perennial
pests. And Midwestern growers should be prepared for yet another year of
soybean aphid invasions. The trend of aphids as perennial pests has
certainly been set.
This newsletter is geared toward helping you know where the aphids may
attack, when and how they can be controlled. We hope you find it useful.
Aphid Suction
Trap Network Shows Infestation Patterns
By Larry Stalcup
If past infestations are any indication, good
aphid-control measures will be critical this summer across much of the
Midwest.
The North Central Regional Soybean Aphid Suction Trap Network, with its
more than 40 test trap locations in 10 states, tracks the tiny terrors
throughout the growing season and into harvesttime. One region of
Minnesota had more than 5,900 aphids in a trap last September, the
largest trap count over two years. And an Iowa test location exploded
with over 3,500 aphids in its trap in August 2007.
Last year was projected to be a light one for soybean aphids. But
estimates were wrong, as was apparent by trap numbers. And even though
entomologists say they can’t predict aphid outbreak levels, the
network is one of the more useful tools for gauging the threat of
soybean aphids. It maps where the aphids were apparent in different
months last year and in 2007. Uncertainties of when and where the aphids
will attack make it important for growers to have a solid integrated
pest management (IPM) control program in place.
“The suction trap network has been useful as a research tool for
helping entomologist estimate the year-to-year variability in soybean
aphid outbreaks,” says Matt O’Neal, Iowa State University Extension
entomologist. “Recently these outbreaks have occurred back-to-back
despite the contrary predictions of the network.
“During the field season, growers may want to visit the Web site,
where the numbers of winged soybean aphids are reported for suction
traps around the Midwest. This may give them some insight into where
aphids are active. However, these traps are not a substitute for
scouting your own fields. Optimum management of the aphid requires
scouting to make the most of a foliar-applied insecticide.”
Traps are located in Illinois, Indiana, Iowa, Kansas, Kentucky,
Michigan, Minnesota, Missouri, South Dakota and Wisconsin. The network
is operated by the North Central Region IPM Center, headquartered at the
University of Illinois and Michigan State University.
Traps are strategically located in areas of widespread soybean
production. State-by-state trap locations with the highest reported
trapped aphid numbers in 2008 compared to the highest in 2007 is as
follows (some locations with few or no captures are not listed):
- Illinois
Perry, 226 on Sept. 26, ’08, after 303 on Aug. 10, ’07
Urbana, 206 on Sept. 26, ’08 after 155 on Aug. 3, ’07
Metamora, 53 on Aug. 15, ’08 after 160 on Aug. 3, ’07
Monmouth, 98 on Sept. 19, ’08 after 40 on Aug. 3, ’07
Morris, 83 on Sept. 12, ’08 after 627 on Aug. 3, ’07
DeKalb, 186 on Aug. 15, ’08 after 266 on Aug. 10, ’07
Freeport, 56 on Sept. 12, ’08 after 328 on Aug. 3, ’07.
- Iowa
Ames, 2,010 on Aug. 15, ’08 after 695 on Aug. 3, ’07
Nashua, 516 on Aug. 22, ’08, after 3,530 on Aug. 3, ’07
Sutherland, 864 on Aug. 1, ’08, after 305 on Aug. 3, ’07
Chariton, 634 on Aug. 22, ’08, after 1,115 on Aug. 3, ’07.
- Indiana
Wanatah, 1,828 on Sept. 26, ’08 after 81 on Aug. 10, ’07
West Lafayette, 45 on Sept. 26, ’08 after 817 on Aug. 10, ’07
Pit, 88 on Sept. 26, ’08 after 283 on Aug. 10, ’07
Farmland, 17 on Sept. 19, ’08 after 36 on Sept. 18, ’07
Sepac, 96 on Sept. 26, ’08 after 7 on Aug. 10, ’07
Columbia City, 6 on Sept. 10, '08 after 53 on Aug. 24, '07
- Kansas
Manhattan, 19 on Aug. 15, ’08 after 9 on Aug. 10, ’07.
- Kentucky
Princeton, 23 on Oct. 3, ’08 after none in ’07.
- Michigan
St. Charles, 457 on Sept. 26, ’08 after 68 on Sept. 28, ’07.
East Lansing, 18 on Sept. 26, '08 after 6 on July 27 and Aug. 10, '07
Kellogg, 4 on Sept. 12 after 83 on Aug. 10, '07
Oceana County, 5 on Aug. 29, '08 after 3 on Aug. 10, '07
Monroe County, 5 on Aug. 22, '08 after 36 on Sept. 28, '07
- Minnesota
Lamberton, 5,926 on Sept. 26, ’08 after only 39 on Aug. 3, ’07
Morris, 1,052 on Aug. 22, ’08 after 46 on Sept. 28, ’07
Rosemount experiment station, 1,029 on Aug. 8, ’08 after 517 on July
27, ’07
Hollandale, 443 on Aug. 15, ’08 after 3,316 on Aug. 3, ’07
Crookston, 190 on Sept. 26, ’08 after 4 on Aug. 17, '07.
- Missouri
Columbia, 141 on Oct. 10, ’08 after 14 on Aug. 3, ’07.
- South Dakota
Brookings, 2,491 on Aug. 22, ’08 after 91 on Aug. 17, ’07.
- Wisconsin
Hancock, 612 on Aug. 22, ’08 after 289 on Aug. 3, ’07
Eau Claire, 215 on Aug. 22, ’08 after 873 on Aug. 3, ’07
Antigo, 292 on Aug. 22, ’08 after 87 on Aug. 10, ’07
Seymour, 226 on Aug. 15, ’08 after 57 on Aug. 3, ‘07
Walmouth, 573 on Aug. 22, ’08 after 789 on Aug. 3, ’07
Arlington, 231 on Aug. 15, ’08 after 366 on Aug. 3, ’07
Lancaster, 495 on Aug. 22, ’08 after 2,340 on Aug. 3, ’07.
For a complete look at the North Central Regional Soybean Aphid Suction
Trap Network, click
here.
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Know What You're
Looking For
 The soybean aphid is a small, yellow aphid with
distinct black cornicles, resembling “tailpipes” on the tip of the
abdomen. This aphid can be found on stem apices and young leaves of
growing soybean plants and on the undersides of leaves of mature plants.
Because there are no other aphid species that develop colonies on
soybeans in North America, it is safe to assume that colonies of tiny
yellow aphids on soybeans are indeed the soybean aphid. Several other
aphid species feed on soybeans, but they are migratory and do not
colonize soybeans.
Monitoring Soybean
Fields
In its National Pest Alert Soybean Aphid booklet, USDA
outlines how the insect migrates from one host plant to another. USDA
points out that it’s not known when the soybean aphid will begin its
migration from buckthorn to the Corn Belt. Soybean fields should be
monitored at specific growth stages rather than calendar date.
Growth stages differ by planting date and other factors that affect
soybean development. Aphid populations build and peak during the period
between late seedling stage V2, or two fully expanded trifoliate leaves,
to blooming stages R1–R2. Colonies concentrate on new terminal
trifoliolate leaves and new leaves on side branches.
In late July, the top growing point of soybean stops and the aphids move
from the top of the plant to middle or lower areas of the canopy to the
undersides of soybean leaves, petioles and pods. Aphids are much smaller
and more yellow in late July than forms found earlier in the growing
season.
From late August to early September the aphid colonies begin to rapidly
multiply again. Honeydew and sooty mold on all plants is evidence of
soybean aphid presence.
For more information on soybean aphid,
click
here.
Speed Scouting Made
Easy
Speed scouting is a sampling method that helps growers
determine if a soybean field is at risk for yield loss due to an
outbreak of soybean aphids. This method will help growers estimate if
soybean aphid populations are reaching the 250-aphid/plant economic
threshold. By going to the link below, growers can learn more about
speed scouting through an online training game.
Click here for the training session Click here
for the training session.
Be Ready To
Apply Foliar Insecticide
Unless there’s a large beneficial insect population,
there’s likely little growers can do to prevent a soybean aphid
outbreak. Matt O’Neal, Iowa State University entomologist, says that
it will be 2010 before aphid resistant soybean lines are widely
available on the commercial market. And although growers have likely
been encouraged to use an insecticide seed treatment, “these products
alone will not protect their fields from soybean aphids. It’s better
to scout and use a foliar-applied insecticide as needed.”
USDA has established recommendations for a soybean aphid spraying
program:
- R1 to R5 growth stages During the period when the soybean
crop is reproductive, an insecticide application may be necessary when
there are 250+ aphids/plant and approximately 80% of the field is
infested and populations are increasing. Sequential scouting in the same
field is necessary to determine if populations are increasing.
- R6 growth stage A higher threshold is required for economic
return during the R6 growth stage. If treatment options are considered,
ensure preharvest intervals of the insecticidal product chosen are met
prior to application.
- R7 growth stage and later
During the R7 and R8 growth stages, there is no economic return on
insecticidal applications.
“Use of insecticides requires careful timing and application,” says
O’Neal. “We continue to recommend applying these products when
populations exceed 250 aphids/plant. Under these conditions, growers
are advised to maximize the penetration of the product into the canopy.
“We have seen a 1-2-bu./acre improvement in yield protection when
insecticides are applied with appropriate pressure and volume, compared
to when insecticides are applied like a herbicide (i.e. with reduced
volume and pressure to prevent drift).”
For a more detailed soybean aphid treatment recommendations, growers and
consultants should contact their local Extension entomologist or crop
chemical provider.
Can 'Natural'
Nitrogen-Fixing Bacteria Protect Soybeans From Aphids?
A team of Penn State University entomologists believes a
careful choice of nitrogen-fixing bacteria may provide soybeans with
protection against soybean aphids. The Asian origin of both is behind
the conclusion.
Soybeans are legumes, or plants that can have a symbiotic relationship
with nitrogen-fixing bacteria – rhizobia – and therefore do not need
additional nitrogen (N) fertilizer. Each type of legume – peas, beans,
lentils, alfalfa – have their own rhizobia.
“Soybeans are from Asia and so there were originally no N-fixing
bacteria that would colonize soybeans in U.S. soils,” says Consuelo De
Moraes, Penn State associate professor of entomology. “The rhizobia
had to be transferred here.”
The soybean aphid is also not native to North America. This pest only
began to infest soybean fields in about 2000. But there are now fully
established pests requiring pesticide applications to avoid the loss of
as much as 40% of the crop. Penn State researchers investigated the
relationship between the type of rhizobia colonizing soybean plants and
the plants' infestation with the aphids.
“Our results demonstrate that plant-rhizobia interactions influence
plant resistance to insect herbivores and that some rhizobia strains
confer greater resistance to their mutualist partners than do others,”
the researchers report in the journal Plant and Soil online.
For more on this story, click
here.
Soybean Growers
Gain From Localized Aphid Alerts
Soybean aphids have rapid reproduction and colonization
rates that can cause them to boom from one to 5,000 on a single plant in
as little as five weeks, according to the University of Minnesota
Extension Web site. Moreover, in favorable temperatures – generally
between the high 70s to low 80s – populations can double in as little
as two days.
With populations able to increase so rapidly, growers, in turn, need
rapid awareness as populations near economic threshold. Going to AphidAlert.com is one way growers can
keep up with the latest information on aphids and other insects. In
addition, growers can sign up to receive free localized alerts when
aphids hit in their area.
“The Web site was created to give growers a one-stop shop for
information on background, scouting and treatment for aphids,” says
Steve Olson, Bayer CropScience insecticide product manager. “They can
also sign up to receive a free alert via text message, e-mail or voice
alert when aphid populations are increasing in their area.”
The alerts, powered by Commodity Update, provide growers a warning that
aphids are on the rise, which is a sure sign that it is a smart time to
scout fields and consider an insecticide to protect soybean yields.
For more information, go to AphidAlert.com
Check Out These
Soybean Aphid Web Sites
USDA Aphid Site – sba.ipmpipe.org/cgi-bin/sbr/public.cgi?host=All%20Legumes/Kudzu&pest=soybean_aphid.
North Central Soybean Research Program Updates – www.planthealth.info/aphids_basics.htm.
North Central Regional Soybean Aphid Suction Trap Network – www.ncipmc.org/traps/index.cfm.
University of Illinois –
www.ipm.uiuc.edu/fieldcrops/insects/soybean_aphids/index.html.
Iowa State University – www.ent.iastate.edu/soybeanaphid/.
Kansas State University – www.oznet.ksu.edu/entomology/extension/InsectInfo/SoybeanAphid.htm.
Michigan State University – www.ipm.msu.edu/soybean/aphid.htm.
North Dakota State University – www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/Soybean_Aphid/sybn_aphd.htm.
Ohio State University – ipm.osu.edu/soyaphid/index.htm.
Penn State University – www.ento.psu.edu/extension/factsheets/soybeanAphid.htm.
University of Kentucky – www.uky.edu/Ag/IPMPrinceton/SoybeanAphid/sbaphidindex.htm.
University of Minnesota – www.soybeans.umn.edu/crop/insects/aphid/aphid.htm.
University of Wisconsin – www.plantpath.wisc.edu/soyhealth/aglycine.htm.
Virginia Tech University – www.idlab.ento.vt.edu/.
Thanks For Viewing
Again, thanks for taking time to read this e-newsletter.
Hopefully it has helped answer some of your questions on soybean aphids.
If you have a particular questions, contact your Aphid Alert editor at
beef2lar@suddenlink.net.
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