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Sudden death syndrome lurking in area soybean fields

Mike Roegge, extension educator for the University of Illinois, shows a soybean plant affected by sudden death syndrome Thursday. (H-W Photo/Phil Carlson)
Posted: Aug. 30, 2014 2:41 pm Updated: Sep. 13, 2014 11:15 pm

By DEBORAH GERTZ HUSAR
Herald-Whig Staff Writer

PLEASANT HILL, Ill. -- A color change first hinted at a problem lurking in area soybean fields.

What had been lush green plants turned yellow, then brown as sudden death moved into the crop.

"You can kind of look over the tops of them and see it," said Roberta Simpson Dolbeare, who farms near Pleasant Hill with her husband, Eric, and serves as District 12 director on the Illinois Soybean Association Board. "Once you know what you're looking for, you notice it more."

Cool, wet weather at planting primed the crop for an outbreak of the disease, then rain in early August triggered the symptoms.

"Some years you see initial infection, then it stalls out and doesn't progress any further along the plant. When that happens, you don't see a lot of yield loss," said Mike Roegge, University of Illinois Extension local food systems and small farms educator. "Other years it continues to progress, kills the plant prematurely and expands in the field to take a larger portion."

What happens this year remains to be seen, but symptoms are widespread across West-Central Illinois, less so in other areas of the state.

Some fields started showing signs two weeks ago, and the affected areas expanded rapidly, which is "not a good sign," Roegge said.

Germinating plants always are exposed to the soil-based Fusarium organism, which causes sudden death. The longer it takes beans to emerge, the better the risk of infection, but "you have to have rainfall at late flowering and early pod fill for it to show up on leaves and plants," Roegge said. "That organism clogs up the vascular tissue in the plant so it can't transmit water and nutrients up to the leaves, so the leaves start dying."

Although not every field is affected by SDS, the ones that are could see losses of 10-20 percent.

"The crops aren't going to be what we thought they might be," Dolbeare said. "Beans are still growing, still producing at this stage. We're going to see some reduction in yield, but how much, I'm not real sure."

Once SDS appears in a field, farmers have few weapons against it.

"There's no resistant varieties, no products that can be used to alleviate the situation. If you have a field in corn for 15 years, that organism still survived. It's a long-lasting, long-lived organism," Roegge said. "The only thing we can suggest people do is in fields where sudden death occurred to plant them later, so emergence is later, but it's kind of a hard thing to accept, too, because when the field is ready, you're going to plant it."

Aside from the SDS threat, soybeans seem to have the makings of a good crop.

"The plants look healthy. Pod development looks good," Dolbeare said. "We'll see what kind of effect (SDS has)."

The area's soybean crop might not be the only one threatened by weather conditions.

Mike Roegge, University of Illinois Extension local food systems and small farms educator, said the corn crop "looked much better a month ago than it does now."

Quincy's Baldwin Field reported rain on 13 of the first 26 days of August, which hasn't helped corn fields.

"We've had more clouds than sunshine in August, and the photosynthesis factory doesn't function very well when it's cloudy," Roegge said.

That potentially puts a damper on yields.

"We'll still have some good yields, but with the soil moisture we have now if we had a lot more sunshine, what could we have had," Roegge said. "No one will complain about corn yields this year, I don't think, but still."

WHAT IS SUDDEN DEATH SYNDROME?

Sudden Death Syndrome is caused by the soil borne fungus Fusarium solani. Soil borne pathogens enter into host plants through the root system. SDS foliage symptoms begin in the upper canopy after reproductive development begins. Symptoms include yellow blotches between leaf veins that turn reddish brown in the center. The leaf veins will stay green. Leaf tissue will dry, and leaves will curl upwards. Typically, SDS is found in patches in a field.

Source: University of Missouri Extension

-- dhusar@whig.com/221-3379