Soybean aphids

Appearance and Life History. The soybean aphid, a native of Asia, has been in the Midwest since 2000 and has quickly become the most serious pest of soybeans in much of Indiana. These aphids are small (less than 1/16" in length), yellow-bodied insects with distinct black cornicles, and may be either winged or wingless. They are typically slow-moving and often found on the underside of the newest growth on a soybean plant.
As with many aphids, the soybean aphid has a complicated life cycle, that requires the presence of its overwintering host, Rhamnus cathartica, or buckthorn. Like the soybean aphid, this plant is an introduced species, and is now found throughout much of the Midwestern U.S. One important feature of the lifecycle is the ability of female soybean aphid to reproduce live, female offspring (clones) parthenogenically during the summer months. This means that soybean aphid numbers can often increase rapidly when conditions are favorable in a soybean field. Soybean aphid are usually found in soybeans from late May through August.
Damage. The soybean aphid feeds using sucking, needle-like mouthparts to extract plant juices. If aphids are present in large numbers, this feeding may cause a reduction in plant vigor and growth rates, as well as leaf puckering, reduced pod/seed counts, and ultimately reduced yield. Severity of damage varies widely depending on pressure and other variables present in the field, although yield losses ranging from 10% to 15% are not uncommon. It is important to remember that aphid damage is exacerbated by other stressors on the plant (eg. drought) and stressed plants are, in turn, more favorable hosts for aphids, resulting in increased reproductive rates. Aphid honeydew, produced as a waste product during feeding, promotes the development of gray, sooty mold on leaf surfaces, reducing photosynthetic capacity of plants