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Soybean Aphid Found In North Carolina
John Van Duyn, NCSU Department of Entomology
V. G. James Research and Extension Center
Plymouth, NC
Soybean aphid in NC
 In September 2005, colonies of soybean aphid,
Aphis glycines, were found in NC soybeans by
crop consultant Stan Winslow.
 He first found the pest on beans in a
Chesapeake, VA field in early September; this
field was sprayed.
 Later in September, fields with low levels of
soybean aphid were found in Camden,
Currituck, and Gates counties (northeastern
NC); populations never reached threshold.
 However, in 2005 many Virginia fields were
treated for SA in the Northern Neck and
Eastern Shore regions.
Distribution of Soybean Aphid in US
 Soybean aphid was first discovered in MN in 2000,
however, a local crop consultant claims to have
seen infestations in 1999.
 That same year it was also found in Wisconsin,
Michigan, Indiana, and Iowa.
 Since that time it has spread very rapidly and is
now found in all major soybean growing states,
as far south as Mississippi and Georgia. Figure 1
shows 2005 distribution of soybean aphid.
FIGURE 1.
Distribution of Soybean Aphid in Asia
Soybean aphid is widely distributed in eastern
Asia (China, Japan, and Southeast Asia to
Malaysia and Indonesia).
 It has been introduced into Australia.
This wide distribution, from temperate to
tropical environments, indicates that it can
adapt to most regions of the US.
 However, the soybean aphid introduced into
the US appears to have come from northern
latitudes since it uses an alternate host on
which to over winter as eggs -- a behavior
common to aphids adapted to cold climates.
Identification of Soybean Aphid
Soybean aphid is a close relative of the cotton
aphid, that is commonly found in NC and is
familiar to many farmers.
Soybean aphid is the only aphid found in the US
that will develop large colonies on soybean plants.
Adult soybean aphids are generally yellow, have
black cornicles (cornicles are tail pipe looking
structures at the back of the body), and are
approximately 1/16 of an inch long when fully
grown.
 Young aphids look like adults without wings but
are smaller.
Adult aphids may be wingless, or, during periods
when they move, develop wings.
Adult soybean aphid (wingless)
Soybean aphid colony showing immature aphids
Colonizing adult (with wings) and new progeny
Soybean Aphid Biology
 Eggs hatch in spring to produce winged females.
 Early season soybean aphids do not mate.
 They move to soybean fields and begin laying
living young (not eggs).
 New aphids are sexually mature in 3-7 days and
new progeny will begin reproducing in 5 days.
 Soybean aphid may infest vegatative stage
soybeans and remain in the crop into the late
reproductive period.
 Later in the season males appear, due to plant
chemical and photoperiod changes, develop
wings, mate with females, and move.
 Adults females lay eggs on several species of
buckthorn bushes for over-wintering; southern
adapted populations in Asia may be active all
year.
Soybean aphid and eggs on a buckthorn bush stem.
Buckthorn bush, soybean aphid’s over-wintering host.
Damage & Virus Transmission
 Soybean aphid sucks sap from soybean plants
and cause plant stress.
 Excess sap sugars are excreted by the aphid as a
liquid called “honeydew”.
 On “V” stage plants aphids are only a threat under
very high populations.
 “R” stage soybeans are more sensitive to aphid
damage, particularly in early reproductive stages
(e.g. R1 – R3); very high numbers of are capable
of causing significant growth reduction, distorted
foliage, and lower seed yields.
 Wang et al. (1996) in China found yields
reductions of 27.8% and plant height decreased
by ca. 8 inches-6 if plants were heavily infested.
Damage & Virus Transmission
 Insecticide spray tests in the US have shown
yield increases ranging from 10% to 20%,
depending on aphid population density,
product used, and other plant stresses.
 Soybean aphid is a known vector of a number
of plant virus diseases.
 For example some domestic viruses vecean
aphid include alfalfa mosaic virus, soybean
mosaic virus, and bean yellow mosaic virus.
Soybean aphid on vegetative plants.
Soybean aphid on reproductive plants and curled leaves.
Soybean aphid damage to leaves.
Soybeans infested with soybean aphid.
Scouting and Thresholds
 In the mid-west, scouting is achieved by
examining plants for signs of aphids (e.g.
disfigured leaves, ants on plants, cast aphid skins,
honeydew on leaves) and aphids in plant
terminals.
 Scouting begins in mid-vegetative stages and
continues to R4 (seeds in pods); it is done weekly.
 Aphids are estimated on the leaves and an
average of five samplings is compared to a
threshold of 250 aphids per terminal leaf.
47 aphids/leaf
11 aphids/leaf
82 aphids/leaf
Soybean aphids at 3 below threshold levels.
An above threshold soybean aphid infestation
(about 150 showing).
An above threshold infestation; ca. 300 showing on this leaf.
Biological Control
 NC entomologists recommend biological control
for cotton aphid management.
 The same approach will reduce populations
soybean aphid.
 Parasitic wasps, insect predators, and a parasitic
fungal pathogen of aphids can exert a powerful
influence to keep aphids in check.
 Basically, all the farmer has to do is to avoid
disrupting the field, by spraying insecticides at
the wrong time.
 Most spraying for corn earworm and other
insects occurs after plants pass the aphid
sensitive stages and will likely not conflict with
aphid management.
Upper – lady
beetle adults
and larva.
Lower – dead
aphids (brown
puffed-up
aphids) killed
by a wasp
parasite.
Soybean Aphid Insecticides
 Soybean aphid is sensitive to a number of
insecticides labeled for soybean in NC.
 Several pyrethroid insecticides that are popular
with farmers, for corn earworm control, will work
on aphids and are labeled for aphids.
 Several phosphate insecticides are also
available.
 Products labeled on soybean for soybean aphid
control include: Asana XL, Baythroid 2, Lorsban
4E, Mustang Max, Penncap-M, and Warrior.
Will Soybean Aphid Become An
Important Pest In NC Soybeans?
 SA is northern-adapted and relies on an alternate overwintering host, the buckthorn bush.
 In NC, the soybean aphid will have trouble surviving
winter in substantial numbers due to the relative low
number of buckthorn plants.
 This suggests that the aphid will have to travel into NC, in
high numbers, to infest vegetative stage soybeans in order
to damage reproductive stage beans.
 This is possible but unlikely, if fields are not disrupted.
 Until soybean aphid adapts and develops an overwintering behavior that doesn’t require buckthorn bushes,
it will likely remain as a minor pest.
 When this happens, soybean aphid on soybeans may be
much like cotton aphid on cotton --- that is, a somewhat
frequent pest.
Acknowledgement
 Information and pictures for this presentation were gathered
from the following sources:
– Soybean Aphid in Iowa – 2005. by M. E. Rice and P.
Pedersen, Iowa State University;
(http://www.extension.iastate.edu/Publications/SP247.pdf);
– Soybean Aphid in Nebraska. by Tom Hunt, University of
Nebraska.
(http://entomology.unl.edu/fldcrops/soybean_aphid04.htm);
– Soybean Aphid. Plant Health Initiative, NCSRP
(http://www.planthealth.info/diag_photo_dp.htm);
– Minnesota Soybean Production, Soybean Aphid. by Ken
Ostlie, University of Minnesota.
(http://www.soybeans.umn.edu/crop/insects/aphid/aphid.ht
m)
– Soybean Aphid. Center for Regulatory and Environmental
Information Systems.
(http://ceris.purdue.edu/napis/pests/saphid/index.html)
THE END
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