Volume
2 Issue
3
June 7, 2005
Soybean Aphids - They’re Baaaack…….
Soybean aphids showed up on soybean in
SE MN last week and WC MN this week. Very low numbers of
aphids have been found on very early plants (V0 / V1) in a
number of locations from the SE corner of the state up to
the Rosemont research & Outreach Center, just south of the
Cities. Aphids were reported from just south of Underwood
(outside Fergus Falls) by Doug Holen. The plants are in V1
and this is very early for us to have aphids in the
region!! Aphids have also been found on soybeans in Iowa,
Illinois, Michigan, and Indiana. This is the earliest
soybean aphids have been found in soybeans in the north
central states. This doesn’t necessarily mean that we’re
in for a big aphid year. Lots of things could still
happen; the weather might not favor aphid reproduction, we
may not get a lot of immigrants contributing to our
populations up here, predator populations may increase and
hit the aphids hard, or fungal diseases might just kick in
and keep aphid numbers low as well. It does mean we should
keep our eyes open and scout soybeans for aphids a bit
earlier than we usually do.
 In
the west central and northwest MN and eastern ND, yield
loss from soybean aphid tends to come from a decrease in
seed size caused by populations that develop later in the
season (R1-R4). However, earlier developing populations of
the aphid will cause stunting of the young soybean plants,
resulting in fewer nodes and fewer pods. This early season
yield loss is often much more severe than the late season
loss we generally experience. Even more reason to ‘Scout
Early – Scout Often!”
Some information on early season scouting for soybean
aphids is available on the Red River IPM website at:
http://www.nwes.umn.edu/ent/redent.html
Remember to look for other signs of aphid presence,
such as cast skins, ants, or lady beetles.
Ian MacRae
U of MN Extension Entomologist
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