Soybean sudden death syndrome

Soybean sudden death syndrome (SDS) has become one of the leading soybean diseases in eastern Nebraska to reduce yield.

“We are seeing a lot of it firing up at this time,” said Dr. Tamra Jackson-Ziems of the University of Nebraska-Lincoln plant pathology department. “The disease tends to be most severe on well-managed soybeans with a high yield potential.”

“The soybean cyst nematode may also cause SDS to develop earlier and become more severe than if the nematode weren’t present,” she said. “So, it’s important to select soybean varieties that are resistant to both SDS and SCN to minimize SDS damage.”

According to Dr. Loren Giesler, head of the UNL plant pathology department, sudden death syndrome was first detected in Arkansas in 1971. It made its first appearance in Nebraska in 2004.

The disease is caused by a fungus that survives the winter as spores in crop residue and soil. It is transferred from area to area when the soil is disturbed releasing the spores, said Jackson-Ziems.

“Anything that moves soil from fields where the disease has been could potentially move the fungus, as well,” she said.

The diseases has two phases: a root rot phase and a leaf scorch phase.

Early in the season, the fungus infects and grows in soybean roots. Infection and colonization are favored by cool, wet soil conditions. Foliar symptoms are more severe after frequent or heavy midseason rains.

“It’s quite widespread this year and it’s likely that the frequent and heavy rainfall supported more disease development,” Jackson-Ziems said.

According to Dr. Jackson-Ziems, symptoms of SDS are easy to recognize.

“It’s a pretty visible disease,” she said. “The leaves turn quickly.”

UNL’s CropWatch states that a key symptom of sudden death syndrome is substantial amounts of root rot and discoloration of roots and crown. Diseased plants are easily pulled out of the ground because of decayed lateral roots and taproots.

Sudden death syndrome is diagnosed by the symptoms on both leaves and roots.

If you suspect sudden death syndrome, you can send infected plants (tops and roots) to the UNL plant diagnostic laboratory. They can perform the tests needed to positively identify the issue, Jackson-Ziems said.

“It’s very important to submit whole plants that include the roots, though, and not just leaves,” she said. “The fungus stays in the roots and sends a toxin up the plant that causes the characteristic leaf symptoms that we recognize as SDS. So, the disease can’t be diagnosed just based on leaves.”

Research shows that corn is a good crop for harboring the SDS pathogen. A clean corn harvest may help reduce the risk of SDS.

“Check with your seed providers for resistant seed varieties,” Jackson-Ziems said. “There have been reductions of 80% using resistant seeds.”

Seed treatment can be effective against SDS and nematodes. But, seed treatments alone have not been effective in controlling SDS. Bayer Crop Science is also working on the problem.

“Bayer is aware of the importance of combating SDS for soybean growers,” said Bayer spokesperson Utz Klages. “Our researchers are working hard to develop new solutions in order to expand and improve our crop protections portfolio.”

The company’s new Iblon technology, based on the fungicidal active substance Isoflucypram, could potentially be a solution; however, it is far too early to make concrete statements today – more research is needed, he said.

“Crop rotation is an additional tool in the fight against SDS,” Jackson-Ziems. “Used in conjunction with resistant seeds and fungicide treatments it can reduce disease incidence.”

Jon Burleson can be reached at jon.burleson@lee.net.

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