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Soybean Aphids: A Perennial Threat?

Kevin L. Steffey Professor and Extension Entomology Specialist Department of Crop Sciences (217) 333-6652 ksteffey@uiuc.edu

David J. Voegtlin Associate Professional Scientist, Center for Economic Entomology, Illinois Natural History Survey (217) 244-2152 dvoegtli@uiuc.edu

The “invasion” of the soybean aphid, Aphis glycines, throughout the Midwest captured the imagination of scientists, educators, soybean producers, agribusiness, and the media for a brief period of time in 2000. The pest disappeared—presumably to buckthorn, its overwintering host—almost as quickly as it had appeared in Illinois in August. During an action-packed four weeks, entomologists in Illinois, Indiana, Michigan, Minnesota, and Wisconsin gathered as much information as possible.

Figure 1. Soybean aphids on soybean leaflet
(photograph by David Voegtlin, Illinois Natural History Survey).

In Illinois, our field surveys revealed that the aphid had dispersed throughout the state. Results from an insecticide efficacy trial showed that some insecticides, although not specifically labeled for control of soybean aphids, significantly reduced densities of the pest. The work continued through the fall (after the aphids had abandoned soybean fields) and winter and into the spring. A large team of research and extension specialists from the College of ACES, the Illinois Natural History Survey, the USDA-ARS, the National Soybean Research Center, and the Department of Geography met frequently to lay plans for research and outreach in 2001.

Early in 2001, we focused primarily on searching for soybean aphids on buckthorn plants, establishing a network of suction traps to sample for flying aphids and establishing protocols for sampling soybeans throughout the season. We also developed plans to establish trials to evaluate insecticide efficacy, determine differences among soybean cultivars in their reaction to injury caused by soybean aphids, and assess yield losses caused by soybean aphids. To document the aphid's distribution (by state and county) and population densities, the "2001 Soybean Aphid Watch" was developed for the Web and is now online at: http://www.pmcenters.org/northcentral/saphid/aphidindex.htm We also developed a suction-trap network reporting form to document captures of flying soybean aphids at seven sites in Illinois: Brownstown, Champaign, DeKalb, Dixon Springs, Freeport, Monmouth, and Perry. Only time will tell if the "invasive" soybean aphid becomes a pest to be reckoned with annually. However, the research team at the University of Illinois is prepared to address many aspects of soybean aphid biology and management very quickly if the pest becomes established.

Figure 2. Suction trap used to sample for flying soybean aphids (photograph by David Onstad, NRES).

Figure 3. 1978 map of distribution of eight species of Rhamnus (buckthorn).

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