Soybean aphids have always been around Ohio, but it has been a while since we have had many fields with high populations. Based on recent scouting, we have noticed increasing populations of soybean aphids. As we go into the critical growth stage of soybean, this is also the most important time to check your fields for soybean aphids and see if you have exceeded the threshold of an increasing population of 250 aphids per plant.
To scout for soybean aphid, walk at least 100 ft from the field edge and count the number of aphids from 5 plants in 10 different locations. If your average is greater than 250 per plant, you’ll need to come back and re-scout 3-4 days later. If the aphid population increased in that time, an insecticide application is recommended. Keep in mind that to accurately determine the threshold, scouting should be performed at least weekly and multiple times a week if aphids are active in fields.
Soybean aphids can cause yield loss up to the late R5 to early R6 growth stage. If an application is necessary, there are several effective insecticides available. Although some soybean aphid populations in the western corn belt are resistant to pyrethroids, we have not seen any evidence of this in Ohio. If you make a pyrethroid application and suspect resistance, contact us (firstname.lastname@example.org, email@example.com) or your local extension educator.