No. 24 Article 5/November 6, 2009

Soybean Aphids Significantly Affected by Fungal Disease This Fall

As I reported in October in the Bulletin, densities of soybean aphids were very impressive this fall as winged aphids left soybean fields in search of their overwintering host, the common buckthorn (Rhamnus cathartica L.). The large and widespread flight of aphids brought speculation and concern that the overwintering population (eggs) of soybean aphids would be significant and result in management challenges next year in soybean fields. Entomologists David Voegtlin (Illinois Natural History Survey) and Christian Krupke (Purdue University) conducted a survey on October 18 and 19 of soybean aphids on buckthorn at sites in southeastern Michigan and northwestern and northeastern Indiana. They observed very low numbers of eggs on the overwintering host. Why? At most observation sites, they found many dead winged aphids on buckthorn leaves. The aphids appeared to have been infected with a fungal disease. David indicated that if other areas of the Midwest are similar, we shouldn't expect this insect to begin 2010 with a large spring flight. I extend my thanks to David and Christian for sharing the results of their survey.--Mike Gray

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