Brian Lang, extension field specialist, Decorah, has been collecting weekly data on soybean aphids from northeastern Iowa during the past four years. The two tables show the percent of soybean plants with aphids and the average number of aphids per plant. Both of these categories show an aphid population that is slightly larger and occurring on more plants than at this same time last year. However, the population does appear to be much smaller than the outbreak population that we experienced during 2003.

Brian also has seen some soybeans with about 1,000 aphids per plant collected near Fort Atkinson, Winneshiek County. The co-op agronomist who found the infestation reported that only part of the field had significant activity, and the population was estimated to average 400 aphids per plant. Field conditions were very dry in this part of the state, which adds to the concern of early season soybean stress and a good environment for aphid buildup.

Percent of soybean plants with soybean aphids, Decorah, Iowa.

Average number of soybean aphids per plant, Decorah, Iowa.