By Janet J. Knodel
Extension Entomologist
Eighty-eight fields were scouted by the IPM Scouts for soybean aphids last week. The IPM scouts in North Dakota and Minnesota found soybean aphids in 60% of the soybean fields surveyed. Percentage of plants infested with soybean aphids ranged from 0 to 100% with an average of 43% of plants infested. The average number of soybean aphids per plant ranged from 1 to 225, and has not increased much from last week’s scouting report. It looks like the severe thunderstorms have had a negative impact on soybean aphid populations in some areas. For example, soybean aphids in our research plot at Casselton decreased after last Thursday’s night thunderstorm and is below the E.T. Scouting is important all the way through the R5 (beginning seed). At the R6( full seed) and later stages, research trials throughout the north central states have not demonstrated a yield benefit to treating soybeans for soybean aphid. The USDA NASS reports that 86% of the soybeans were blooming (R1), and 51% setting pods in North Dakota (USDA NASS News Release – July 27, 2015).
