Fighting a Top Yield Robber: Top Tips for Controlling Sudden Death Syndrome

KEY TAKEAWAYS:

  1. Sudden Death Syndrome (SDS) accounts for millions of bushels of soybean yield losses in the United States each year, although growers may not even realize this yield robber has infected their fields.
  2. While above-ground, foliar symptoms are the most obvious signs of SDS, some of the most serious consequences of the disease occur in the below-ground phase that triggers root rot.
  3. ILeVO® seed treatment from Bayer offers innovative, exclusive technology that manages both the above- and below-ground phases of SDS. On average, growers are seeing a 2 to 10 bushel-per-acre yield advantage when adding ILeVO to their fungicide/insecticide base package.

“There’s nothing you can spray to control SDS. By the time you see above-ground symptoms of SDS, it’s too late.”

When Peter Bixel noticed bronzing on some of the leaves in his soybean fields near Kanawha, Iowa, he wasn’t exactly sure what was going on. Upon closer inspection, the discoloration turned out to be sudden death syndrome (SDS).

“The pockets of bronzing were ugly,” says Bixel, a soybean and corn producer in northern Iowa. “There’s nothing you can spray to control SDS. By the time you see above-ground symptoms of SDS, it’s too late.”

Often appearing as an isolated spot within a field, SDS can expand rapidly to infect other areas. SDS attacks soybean plants in two phases – below ground at the root and above ground within the leaves. Because the pathogen overwinters in the soil, it can spread with each new growing season, especially under conditions of high soil moisture.

Sudden Death Syndrom Development Cycle

SDS accounts for millions of bushels of soybean yield losses in the United States each year. “When I talk to farmers and agronomists, they feel SDS is causing even more yield loss than soybean cyst nematode (SCN), which has been the leading cause of yield loss in soybeans,” says Daren Mueller, an Iowa State University (ISU) Extension field crop pathologist.

Severe SDS can result in yield losses greater than 50%, according to the University of Minnesota. “I’ve seen yield losses of 25 to 40 bushels per acre from SDS,” says Bixel, who also serves as the SciMax Solutions team leader for MaxYield Cooperative’s Information Management Division.
Even worse, once the SDS fungus is present in a field, it does not go away.

“Just because you can’t see it doesn’t mean SDS isn’t there”

SDS shows no signs of slowing down

First seen in Arkansas during the early 1970s, SDS has spread to most of the soybean growing areas in the Midwest and shows no signs of slowing down. While some SDS symptoms are visible, others can be hard to spot.  

“Just because you can’t see it doesn’t mean SDS isn’t there,” said Matt Keel, a MaxYield Cooperative seed solutions specialist. He estimates that 80 percent of the fields in the co-op’s trade territory are affected by SDS. “It’s a problem that keeps creeping up and causes serious yield losses.”

Is it brown stem rot or SDS?

Early symptoms on leaves range from mosaic patterns to a yellowing appearance between the veins. These spots typically expand between veins to become brown lesions surrounded by chlorotic areas, and the leaves may be cupped or curled. Leaves detach from the petioles as the disease progresses. This reduces the plant’s ability to photosynthesize and provide nutrients to promote pod fill, which results in aborted pods and reduced yields. 

ILeVO treated vs untreated soybean plants: below ground vs above ground

 

Brown to grey discolored areas also develop in the vascular tissue of the lower stem and can typically be seen by cutting into the stem of fresh plants. While SDS can look similar to brown stem rot (BSR), it’s fairly simple to distinguish between the two diseases. With SDS, the pith within the stem remains white. The pith will be brown and discolored, however, if BSR is present.

soybean roots infected with SDSSDS can infect plants within 72 hours of planting

Infection can occur within 72 hours of planting

While above-ground, foliar symptoms are the most obvious signs of SDS, some of the most serious consequences of the disease occur in the below-ground phase that triggers root rot. SDS can infect plants within 72 hours of planting, Mueller says. By attacking the roots, SDS slashes yield potential by rotting the plant’s root system throughout the growing season, limiting plants’ water and nutrient uptake.

While SDS infection of the roots occurs early in the season, above-ground symptoms of SDS usually don’t develop until late July or in August. It’s possible the above-ground symptoms may never appear.  “In some cases, SDS can rot the roots without showing any symptoms on the leaves,” says Mike McCarville, a Bayer seed growth tech service representative.

Rotating from soybeans to corn will not reduce risk of SDS, since corn residue plays a role in SDS severity, Mueller says. To complicate matters, SDS may appear earlier and can be more severe in fields infested with soybean cyst nematode (SCN). While these two below-ground yield robbers are often overlooked, SDS and SCN result in a total economic loss of $1.6 billion per year (based on USDA 2016–2017 marketing year projection for average soybean price of $9.10 per bushel).

“You almost have to assume that if you have SDS or SCN, you probably have both,” says Jason Bond, Southern Illinois University plant pathologist.

Conditions that influence SDS

SDS development is favored not only by SCN, but by early planting and susceptible soybean varieties. Since many Midwest soybean fields are planted prior to May 20, the risk for SDS rises because of cooler soil temperatures.

“Abundant rainfall drives higher incidence and severity of SDS.”

SDS also thrives in wet conditions and poorly-drained, compacted soils. “Abundant rainfall drives higher incidence and severity of SDS,” Bond notes. “At this point, the only thing that could reduce the impact of SDS is a very dry July and August.”

While SDS symptoms may be more or less apparent some years than others, depending on weather conditions during the growing season, once the disease is in a field, it stays there. There is no cure for SDS, which must be monitored and managed consistently.

Why SDS-resistant varieties aren’t enough

Although SDS cannot be eliminated, there are ways to address this challenge and prevent substantial yield loss. Proper SDS management starts by selecting SDS-resistant varieties. Be aware, though, that there are still many susceptible varieties on the market.

“More than 40 percent of varieties sold have some level of resistance, but not all soybean varieties have been adequately screened for SDS resistance,” Bond says. While SDS-resistant varieties aren’t immune to the pathogen, SDS symptoms are less severe than with susceptible varieties, he notes.  

Control below- and above-ground SDS symptoms with ILeVO

Combining resistant seed varieties with the right seed treatment is critical to helping seedlings get the best start possible start and reduce the risk of SDS infection, especially as growers continue to plant in earlier, wetter conditions.

Select seed treatments offer an additional management option for SDS and complement the genetic resistance being deployed, Bond says. ILeVO seed treatment from Bayer offers innovative, exclusive technology that manages both the above- and below-ground phases of SDS. ILeVO controls the Fusarium pathogen that causes root rot at the initial infection site before symptoms become visible. This powerful seed treatment also complements current genetics, improving the yield potential of SDS-resistant varieties.

Unlike other seed treatments, ILeVO is also the only solution for SDS that also provides activity against nematodes. This protection in the seed zone produces healthier plants for higher yield potential.

On average, growers are seeing a 2 to 10 bushel-per-acre yield advantage when adding ILeVO to their current seed treatment package.

On average, growers are seeing a 2 to 10 bushel-per-acre yield advantage when adding ILeVO to their current seed treatment package. “We’ve done many trials with ILeVO in the past couple years and have seen it give a 4- to 9-bushel yield advantage,” says Keel with MaxYield Cooperative in Iowa.

Because ILeVO protects seeds from the moment they’re planted, crops can be planted earlier in the season with less risk of SDS and SCN damage – allowing the opportunity to optimize yield potential and profit potential. By offering protection from disease pressure throughout the growing season, including above- and below-ground SDS control, ILeVO promotes the development of stronger root systems and healthier foliage, which contribute to stronger stands.

“University trials show a consistent response in terms of lower SDS and higher yields by using ILeVO, in fields where SDS develops,” Mueller says.

The ability ILeVO has to manage above-ground SDS symptoms and below-ground root rot sets it apart from other seed treatments.

ILeVO helps protect growers’ bottom line  

The ability ILeVO has to manage above-ground SDS symptoms and below-ground root rot sets it apart from other seed treatments, McCarville says. “It’s a powerful tool to manage SDS and protect yield potential as SDS continues to spread across soybean-growing regions.”

This proven seed treatment also helps protect the bottom line. Once growers try ILeVO, they often put it to work on all their soybean acres. “Two years ago in a Midwestern field trial we split a planter where half the soybean seeds were treated with ILeVO,” McCarville says. “After this grower saw the positive results from ILeVO, he wanted all his soybeans treated with ILeVO from then on.”

Convenience and proven SDS protection that starts early in the growing season are big advantages of ILeVO, adds Bixel, who tried ILeVO in 240 of his soybean acres in 2016. The return on investment has encouraged Bixel to use ILeVO on all his soybean acres going forward. “ILeVO is a great investment,” he says. “It’s exciting that we finally have a proven solution like this to help control SDS.”



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