Soybean aphids attack: Does it pay to spray low populations?

After a relatively quiet June and July, soybean aphid populations are building in certain parts of the state. Although data may not be present, soybean aphids are likely to be present across the state. Aphid populations greater than 250 have been reported in Iowa. However, populations are spotty with heavily infested fields near those with much lower populations. Brian Lang, Iowa State University Extension (ISUE) field crop specialist in Winneshiek County, reports fields with several thousand aphids per plant, with neighboring fields below threshold