While scouting soybean fields near Volga, SD this week, we observed several soybean aphid hotspots. Although these populations are well below the economic threshold of 250 aphids per plant on 80% of the scouted plants, it is an important reminder that soybean aphid populations can appear and increase very rapidly. Most of the soybean aphids we observed were in very small groups of 1-10 aphids per plant. However, we also observed some plants with colonies of 30-70 aphids with ants tending them, which indicates the colony has been established for some time.
In addition to the soybean aphids, we also observed potato leafhopper nymphs. Although these aren’t a concern for soybean production, they can easily be confused with soybean aphids during their early instars. When scouting soybean be sure to get a positive identification of the insects. One easy way to determine what you’re looking at is whether or not it moves quickly on the leaf. Soybean aphids are sedentary while the potato leafhopper nymphs move around more rapidly.
To reduce time spent scouting this season, consider using speed scouting for soybean aphid populations. There is a printable worksheet for this method of scouting. Alternatively, there is a phone app called Aphid Speed Scout that can also be used in place of the worksheet.