Eyes on Beans

SDS Symptoms Surfacing in Early Planted Soybeans

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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SDS starts in the roots of young soybean plants and produces interveinal chlorosis late in the season. (DTN photo by Pam Smith)

ROCKVILLE, Md. (DTN) -- Only time -- and scouting -- will tell if sudden death syndrome (SDS) is lurking in the roots of your soybeans.

"Foliar symptoms of SDS have been starting earlier than ever this year," warned Burrus Seeds agronomist Stephanie Porter. "But we're at a point where not many people are seeing it from the road yet."

As early as June, Porter had a hunch that the disease might be hiding in the soybean fields in her coverage area of Missouri, Illinois and southern Wisconsin. Spring conditions this year reminded her of the 2014 growing season, when SDS outbreaks were widespread across the Midwest.

Sure enough, a comparison of climate data between the two years revealed an ominous similarity in the Midwest and Great Lakes region. In both years, April-to-May average temperatures hovered below 60 degrees Fahrenheit and rain storms dropped up to 12 inches of rain.

These conditions are perfect for the fungus that causes SDS. It thrives in cool, wet soils, where it infects the roots of young soybean plants. The disease's root damage becomes clear late in the season, often when rain flushes the toxins up into the plant. Leaves show a striking phenomenon known as interveinal chlorosis, where the leaf tissue between veins turns yellow and then brown. Entire plants, which appeared healthy just weeks before, can wither and die.

Fortunately, a key difference between the 2014 and 2016 planting season means SDS damage will likely be less pronounced this year, Porter said.

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"So many growers missed a small planting window in late April this year and the next planting was really late, which might prevent an SDS outbreak," she told DTN.

Those who did get beans planted in late April or very early May should be on the lookout for the disease.

Don't rely on windshield surveys alone, Porter warned. "I'm seeing a lot of different diseases out there," she said. White mold, stem canker, brown stem rot and even Phytophthora root rot can be confused with SDS, but inspecting the stem of the infected plant is an easy way to diagnose the problem from your truck bed.

In a soybean plant with SDS, the "pith" or center of the stem, will be clearly white, Porter said. If the pith is dark, the symptoms are more likely from brown stem rot. Stem canker will produce dark cankers -- or lesions -- on the outside of the stem near the petioles. Phytophthora will also cause stems to darken on the outside, but near the soil line. White mold, as the name suggests, will produce a fuzzy, white coating on the stems.

This year may give a seed treatment called ILeVO another chance to shine. The seed treatment is produced by Bayer CropScience and is designed to shield roots from the SDS fungus, Fusarium virguliforme.

Over the course of five years and 350 company and university field trials, ILeVO has shown an average yield gain of 4.6 bushels per acre. When SDS symptoms are light, the yield bump drops down to 2.9 bpa and in severe pressure, it rises as high as 10 bpa, according to a company presentation.

The seed treatment comes at a price, however. Porter said prices often run around $16 per unit. At current soybean prices, a yield bump of 2 bushels would just barely cover the cost, she noted.

As a result, the treatment is best targeted to early planted fields with a history of the disease.

For more information on SDS this year, see an article by Porter for the Illinois Soybean Association here: http://bit.ly/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(PS/AG/CZ)

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Emily Unglesbee