Soybean aphids: Do I have to throw insecticides in the tank?

The current recommended economic threshold is 250 aphids per plant with 80% of the plants infested.

Soybean aphids on leaves
Soybean aphids on leaves. Photo by Chris DiFonzo, MSU Entomology.

Soybean aphids can infest soybean plants, causing yellowing, distorted leaves and stunted plants. These insects like to stay on the top of the plants on the newest growth, especially in the folded leaf that hasn't emerged yet.

In Michigan, soybean aphids overwinter on buckthorn trees, and after one to two generations, the winged aphids come out and colonize soybeans. Since soybeans in most of Michigan came up later this year, Michigan State University Extension entomologist Christina DiFonzo believes that in 2019, soybeans emerged after the soybean aphids moved off the buckthorn trees and for this reason they did not get colonized yet. Later in the year, there is a possibility that soybean fields will get colonized, mostly by aphids coming from neighboring fields or even from Minnesota or Wisconsin.

You should be using the threshold of 250 soybean aphids per soybean plant when scouting your fields. Aphids’ presence about the threshold levels would indicate that an insecticide application might be beneficial. An infestation situation that you would need to spray would be when the plant is covered with bright green aphids.

Based on DiFonzo’s experience, spraying pesticides when an infestation occurs early in the season doesn't pay off. Even whre there are 50-100 aphids per plant, biocontrol agents such as ladybugs and lacewings can do a good job controlling soybean aphids.

If you are interested in learning more about this topic, watch this short video. Also, don’t miss DiFonzo give a live update on insect management on the Aug. 1, 2019, Field Crops Virtual Breakfast meeting from 7-7:30 a.m. Scroll down to read more about how to join.

Join the Field Crops Virtual Breakfast meeting series

In agriculture, things can change fast. To help growers keep up with weather, pests and crop management issues, the MSU Extension field crops team is holding free Virtual Breakfast sessions every week during the growing season via Zoom video or phone conference. These virtual meetings take place every Thursday morning from 7-7:30 a.m. starting April 25 through Sept. 5, 2019.

Participating is easy!

You can join using your computer or mobile device (audio and visual) following the Zoom link: Or, call in from your phone (audio only) by dialing 669-900-6833 and enter meeting ID 552-324-349.

To receive a weekly email reminder of the Virtual Breakfast, sign up at Participants receiving emails can opt in or out at any time.

Can’t make it Thursday morning? Watch the recording!

For those who cannot join on Thursdays at 7 a.m., the Virtual Breakfast sessions will be recorded for later viewing with closed-captioning on the Field Crops Virtual Breakfast webpage. Podcasts are also available on the iTunes and Spotify.

Don’t forget to follow us on social media. Stay up-to-date on what is happening in Michigan field crops by liking the MSU Extension Field Crops Facebook page or following @MSUEFieldCrops on Twitter.

Scheduled topics and dates

Note that these may change to cover breaking pest and weather situations.

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