Pest Profile

This is a very small, yellowish aphid with black cornicles. During vegetative growth look for aphids under young upper leaves, petioles and stems. Later in the season when the soybeans are in the reproductive stage look for aphids in the mid-canopy leaves and on the stems and pods. Soybeans in the early reproductive period are probably the most vulnerable to aphid attack. Other species of aphids occasionally infest soybean, but the soybean aphid is the only species to develop very large colonies.

The soybean aphid has been present in eastern Kansas since 2002 and was widely distributed throughout soybean-growing regions of the state by 2004, with populations approaching damaging levels in some areas. From 2005 to 2007 soybean aphid populations were relatively low with no reports of serious injury. However, in 2008 populations were again well established in northeast Kansas. Cool weather during the summers of 2004 and 2008 is thought to be responsible for the problems in those years. Temperatures The growth of soybean aphid populations is inhibited at temperatures above 75˚F within the plant canopy. Thus cool summers will have a higher potential for soybean aphid problems and weather forecasts should be considered when sampling data is evaluated.