No. 7 Article 2/May 20, 2011

Low Numbers of Soybean Aphid Colonies on Buckthorn Confirmed

In a recent survey (May 11-13), David Voegtlin, an emeritus entomologist with the Illinois Natural History Survey in Champaign, confirmed that spring colonies of soybean aphids on buckthorn are at low levels. He indicated that he did not anticipate finding many colonies given the low densities of winged aphids caught last fall in the suction trap network that he coordinates. Dave was able to examine buckthorn plants for aphids near Rome City (northeastern Indiana), Irish Hills (southeastern Michigan), Kellogg Forest (near Battle Creek, Michigan), Calumet (south of Chicago), Joliet, and the Quad Cities vicinity. He has sampled these areas in previous years and noted that Rhamnus cathartica (common buckthorn) plants are abundant.

The results from Dave's survey revealed some soybean aphid colonies at the Kellogg Forest and Quad Cities sampling sites. Near Rome City, only one colony was found after a very thorough search. No colonies were detected at any other location. No winged aphids were observed in any of the colonies, only wingless adults and nymphs. Dave also indicated that he did not find any natural enemies in the colonies. He speculated that low numbers of aphids make it very difficult for natural enemies to find the colonies.

These observations, along with the delayed planting of soybeans this spring, suggest that soybean aphids will not be much of a threat through the early portion of summer. If cool growing conditions occur throughout the summer, perhaps late in the growing season, soybean aphid numbers could begin to surge. For now, these results, shared generously by Dave, represent good news for soybean producers.--Mike Gray

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