The soybean aphid is currently the only aphid species that infests
and multiplies on South Dakota soybeans. 

It is small but still can be seen with the naked eye.  The wingless
form is about 1/16 inch long when fully grown and may be yellow
to yellow-green in color.  A newborn soybean aphid is
about 1/4 the parent’s size.

The soybean aphid has two black-tipped “tailpipes” or cornicles
that can be seen easily under a hand lens.  The winged form of
the aphid has two pairs of delicate transparent wings and a
general blackish coloration.  Once on buckthorns, soybean
aphids take on a more bluish color but can still be identified
with their black-tipped “tailpipes.”

Soybean aphids assume several different forms, depending on
season and plant condition.  Winged aphids are commonly
seen in late summer or early spring as aphids migrate between
soybeans and buckthorns.

Once on a soybean plant, overcrowding also may force the
soybean aphid to produce winged forms, perhaps to enable
it to colonize other less-infested soybean plants in the field.
 

   |  SD Soybean Aphid Biology  |

Prepared and posted  by Mike Catangui on December 23, 2002.  Last updated on Friday May 2, 2003.