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Start Scouting For Soybean Aphids

Start Scouting For Soybean Aphids

Populations can increase quickly under the right conditions. ISU entomologists recommend you scout fields once a week and treat when population reaches economic threshold.

Soybean aphids have been almost hard to find in Iowa the last few summers. Growers have benefitted from low statewide populations of this insect pest because these low populations have saved on insecticide application costs. However, this year there have been reports of aphids in Iowa since early June. Aphids have been detected in all parts of Iowa except the southeastern region.

"At this time, soybean aphid densities are low and the percent of plants infested also remains small," says Erin Hodgson, Iowa State University Extension entomologist. "But this aphid can quickly reach outbreak levels under the right growing conditions, so I encourage all soybean growers to remain diligent about scouting this year."

Soybean aphids are highly migratory after soybeans begin to bloom and are able to move within and between fields, she explains. Begin scouting soybean fields at bloom to see if soybean aphids are present. Scout every soybean field, even if a seed treatment was used and a resistant variety of soybean was planted.

Scout soybean fields once a week to keep an eye out for aphids

"Keep monitoring you soybean fields weekly from now through seed set to protect the yield," advises Hodgson. "Regular monitoring will tell how fast aphid populations are growing and will help you make timely foliar applications of insecticide if needed. Remember, the economic threshold for soybean aphid is 250 aphids per plant during flowering through seed set. When the population reaches 250 aphids per plant, that's when you need to spray with an insecticide treatment. Don't spray before it reaches that economic threshold."

Click here for an online version of a fact sheet on aphids, prepared by ISU entomologists Erin Hodgson and Matt O'Neal. 

In addition, the Iowa Soybean Association and Iowa State University have recently published a new edition of the Soybean Aphid Field Guide. Click here for an online version. Hard copies can also be obtained by calling ISA at 800-383-1423.

Updated edition of Soybean Aphid Field Guide is now available

Authors of the Soybean Aphid Field Guide are ISU Extension entomologist Erin Hodgson and ISU research entomologist Matt O'Neal. 

O'Neal says, "Every year we learn more about the biology of soybean aphids and new ways to prevent this pest from causing yield loss. These insights have been made possible through funding from the soybean checkoff program which helps pay for the research. We have incorporated these discoveries and tools into the revised edition of the guide in an effort to return this checkoff-funded research back to soybean farmers."

Hodgson adds, "The second edition of the Soybean Aphid Field Guide is expanded in every section. We incorporated research information from around the region and developed a more comprehensive management program for aphid control. We encourage soybean growers to use multiple tools to protect soybean yield against the soybean aphid."

How about planting aphid resistant soybean varieties? Do they work?

One of the biggest additions to the toolbox of aphid management strategies is aphid-resistant soybeans. The guide includes a review of the research that led to aphid resistance becoming a common component of soybean genetics for many current and future commercial soybean varieties. David Wright, ISA director of contract research, notes, "This resource is a must-have for all Iowa soybean producers. It is the most comprehensive reference guide available for sustainable management of Iowa's most serious soybean insect pest."

Funding for printing and distribution of the guide was provided by the Iowa soybean checkoff and ISU Extension. Printed copies of the Soybean Aphid Field Guide can be obtained by contacting the Iowa Soybean Association at 800-383-1423; they can also be ordered from the ISU Extension Online Store at or by calling 515-294-5247. The guide can also be viewed online at

TAGS: Extension
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