Plant Health Initiative

Soybean aphid distribution

 

Soybean aphid - year of first detection. Aphis glycines has now been detected in over 20 states. Click image to view a larger version.

Since the initial identification of the soybean aphid in Wisconsin, Illinois, and the Great Lakes area in 2000, the soybean aphid has spread into more than 20 states and 3 Canadian provinces. 

Aphid populations are known to be highly variable from field to field, and from year to year.

 

Soybean Aphid Suction Trap Network

One way to predict if aphids will be problematic in any particular year is by monitoring winged soybean aphids as they fly between soybean fields during the summer and to buckthorn in the early fall.

A suction trap network has been established across the Midwest to monitor winged aphids. The network consists of 42 suction traps operating in 10 states. The traps are basically big tubes roughly 25 feet tall – high enough to catch winged, migrating aphids. At the base of each tube is a jar filled with preserving fluid. Fans suck aphids into the tube, and aphids are preserved in the jar. Every week, researchers replace the jars and count the number of soybean aphids. Results are reported on the Regional Soybean Aphid Suction Trap Network website.

Suction traps are a means to track aphid overwintering flights. Fall flight activity may indicate the size of the overwintering, and following-season, soybean aphid population. Trap captures can be viewed at the Regional Soybean Aphid Suction Trap Network

Researchers have found that when soybean aphid populations are high, exceeding 1,000 aphids per plant, large numbers of winged aphids are trapped in July and early August, but numbers drop off dramatically by late August. Thus, small numbers of male and female winged aphids migrate to buckthorn, which will result in fewer overwintering eggs. This may lead to smaller numbers of aphid colonizing soybeans the following spring.

When soybean aphid population densities are lower, small numbers of winged aphids are trapped during July and August. In September, however, significantly more aphids (nearly 40 times more than in high aphid years) are typically trapped. Large numbers of winged aphids captured in the fall suggest large numbers of eggs will be laid on buckthorn. This may result in large populations of aphids the following spring.

Suction traps help estimate overwintering population densities, providing insight into yearly population variation. However, other factors may influence whether any particular year or location will have an outbreak of soybean aphid.

In addition to identifying all the aphids of agricultural interest, staff in Dr. David Voegtlin’s lab in Illinois also identify native aphids that are encountered.

 

Resources

Soybean Aphid Field Guide 2nd Edition - Iowa State University (pdf)

Assessing the Invasion by Soybean Aphid: Where Will It End? R. C. Venette and D.W. Ragsdale, 2004. Annals of the Entomological Society of American 97: 219 - 226 (pdf)