Menu

Soybean Aphid Numbers on the Rise

Since 2000, soybean aphid has been the primary soybean insect pest in Iowa. Infestations are sporadic and unpredictable, but this insect has the ability to cause significant yield loss during periods of optimal reproduction. Several notable infestations have been reported, particularly in north-central Iowa, this week, and therefore scouting to determine population densities is strongly encouraged. Fields that have a fairly uniform infestation with low densities (e.g., 50% of plants infested with an average of 40 aphids per plant) should be closely monitored in August.

Biology
Soybean aphid is the only species in Iowa that will colonize soybean. After developing on their overwintering host, buckthorn, winged adults will migrate to soybean and potentially product 15+ generations. Initial infestations in soybean are patchy and located near field edges, but winged aphids can quickly disperse within and between fields. Long and short distance immigration is more likely after bloom. Aphids prefer to feed on the undersides of leaves and will colonize on the newest leaves. If a large colony develops and leaves are crowded, soybean aphid will feed on stems.

Management 
According to my efficacy evaluations, most products labeled for soybean aphid are efficacious. Some foliar insecticides have a 60-day preharvest interval, so check the label and the calendar when making product selections. At this time, product choice is not as critical as getting sufficient coverage. With any foliar application, strive for the highest knockdown possible to avoid resurgent aphid populations. Ideally, increasing volume and pressure will generate small droplets that should make contact with the aphids on the undersides of leaves. For ground applications, use 20 gallons of water per acre and 40 pounds of pressure per square inch.

Scouting
With the potential of many overlapping generations in a field, scout weekly from plant emergence until seed set to assess population dynamics. The economic threshold for soybean aphid is well established for the north-central region. Consider a foliar application when the average density exceeds 250 per plant. Populations should be increasing and most of the plants have to be infested (>80 percent) in order to justify an application. This threshold is appropriate until plants reach mid-seed set. Alternatively, consider using a binomial sequential sampling plan, Speed Scouting, to help make treatment decisions. Find blank forms here.

Source: Iowa State University

Recent News

Senate Passes USMCA
1/17/2020

Just one day after the U.S. and China signed a Phase One trade deal, the Senate passed the U.S.-Mexico-Canada Trade Agreement (USMCA). Donald J. Trump ✔@realDonaldTrump One of the greatest trade deals ever made! Also good for China and our long term relationship. 250 Billion Dollars will be coming back to our Country, and we are […]

U.S., China Sign Phase One Trade Deal-Agricultural Purchases Included
1/16/2020

Financial Times writer James Politi reported on Wednesday that, “The US and China have signed an agreement to pause the trade war that has weighed on the global economy for nearly two years, while leaving in place tariffs on hundreds of billions of dollars of Chinese imports. “The so-called phase one deal signed at the White House on Wednesday offers […]

Did That Really Just Happen? USDA Revisions to the 2018/19 Corn Balance Sheet
1/15/2020

The USDA released a number of important reports for the grain markets on January 10, 2019, including the quarterly Grain Stocks report, Annual Crop Production Summary, and the monthly World Agricultural Supply and Demand Estimates (WASDE) report.  In addition to all the estimates that garnered headlines, the USDA also released much less noticed revisions to production, ending stocks, and feed […]

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now