The life cycle of a soybean aphid begins on a buckthorn.  Buckthorns
(Rhamnus cathartica) are very common shrubs in the South Dakota
landscape.  They grow underneath trees in shelterbelts as shrubs or
as small trees along fencelines or field margins of open fields.
Some homeowners grow buckthorns as an ornamental or shelter
plants around the house and buildings.

Winged female soybean aphids return to buckthorns during the fall
to give birth to a generation of egg-laying wingless females. Male
soybean aphids develop on soybeans and fly into the buckthorns in
search of the wingless females. The eggs laid beside buds on the
buckthorn twigs survive the winter but the aphids themselves are
killed off by freezing temperatures.

In the spring, the overwintered eggs hatch into nymphs, and after
two generations of wingless aphids on buckthorns a generation
of winged females migrates from buckthorns to soybeans as soon
as the soybeans emerge from the soil.

Once on the soybeans, the winged aphids give birth to numerous
wingless female aphids that, in turn, give birth to numerous other
wingless aphids.  A newborn aphid grows by molting several times
and can start bearing live young aphids within a week.  Winged
aphids are only produced if there is a need for long distance
migration such as when the host soybean plant become over-
crowded, or when it is time to go back to buckthorns in the fall.
 

   |  SD Soybean Aphid Biology  |

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