Sudden Death Syndrome Appearing in Many Iowa Soybean Fields

Sudden death syndrome is a yield-robbing disease that's showing up in many Iowa soybean fields this year. Depending on the soybean variety, it can cause 100% yield loss.

Rod Swoboda

Published: Aug 16, 2010

Sudden Death Syndrome is disease of major concern for soybean growers due to its ability to significantly reduce yields. "Depending on the soybean variety, it can cause slight to 100% yield loss, and it is one of the top four yield-robbing soybean diseases," says David Wright, director of contract research and strategic initiatives for the Iowa Soybean Association.

Iowa State University Extension field agronomist Mark Licht says growers are starting to see signs of SDS in their fields this growing season. He covers parts of central and west-central Iowa. "We started seeing SDS show up in central and west-central Iowa around the first of August. Early in the week, it was fairly mild and at the end of the week, we were seeing places in some fields that were quite severely affected. The loss began with the yellowing of the leaves and went straight into dropping of the leaves and seeing the death that occurs from that."

Why Is SDS exploding this year? Weather conditions favor it

The disease is spreading more than most people expected this year, says Wright. SDS has also shown up in eastern and northern Iowa, and in Illinois and Minnesota. It's developing in areas where it has not been in the past, and Licht says weather is a major factor.

"SDS is typically found when we have periods when it's really wet, especially if it's cool and wet shortly after planting," explains Licht. "In much of Iowa, we have been really wet ever since that cool period we had in early May. For us to see SDS in the lower, wetter areas where we have compacted soils should be of no surprise because we have had conditions nearly perfect for SDS to show up."

Fungicides do not help with SDS so there's not a lot growers can do this season. Licht advises farmers to think ahead to the next year by scouting now and accurately diagnosing the disease in the field, and keeping records of where the disease is located and on which soybean varieties.

Applying foliar fungicides are of no help with this disease

So what can you do to manage SDS? "It is good to take note of the areas in the field that are more severely affected, and take note of the soybean varieties that are planted out there and how they are responding—how tolerant or susceptible they are to the pathogen," Licht says. "Keeping an eye on these two things is good because when we start planting for the 2011 season, we'll know we should target certain soybean varieties that are known to have a higher tolerance. You should plant these varieties in areas of fields or in entire fields that have had SDS problems in the past. Additionally, fields that are more severely affected can be planted a little later when the conditions for SDS infection are less risky."

Licht urges farmers to watch their fields for SDS showing up this year and then begin a dialogue with Extension specialists and seed company agronomists to get a management and seed selection plan in place for the next year.

Note the difference between SDS and other soybean diseases

Be sure you know how to identify SDS correctly. Don't confuse the symptoms with brown stem rot or other problems, says Licht.

SDS has a classic appearance of yellowing between the leaf veins. As the symptoms progress the yellowing turns necrotic and eventually the leaf dies and drops to the ground. Be sure to split a few stems open lengthwise with a knife to distinguish SDS from brown stem rot, which will have a discolored pith (inside of the stem). SDS tends to be more of a problem in compacted and low lying field areas that hold moisture.

Click here for an Iowa State University Integrated Crop Management Newsletter article that has more details about SDS: how to scout for it and manage it.