Sudden Death Syndrome in Soybeans

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Soybean Sudden Death Syndrome

How to Identify Sudden Death Syndrome

Geographic Impact of Sudden Death Syndrome

Timing of Sudden Death Syndrome

Lifecycle and Distribution

How to Manage Sudden Death Syndrome in Soybeans

Learn More About Sudden Death Syndrome in Soybeans

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Overview

Sudden Death Syndrome (SDS), a disease caused by the fungus Fusarium virguliforme, poses a significant threat to soybean crops globally.

SDS primarily targets the leaves and roots of the soybean plant. The fungus invades the roots early in the season, causing root rot. As the disease advances, it produces toxins that travel to the leaves, leading to leaf scorch and defoliation.

The toxins generated by the SDS fungus disrupt the plant's normal physiological processes, interfering with water and nutrient uptake, photosynthesis, and overall growth and development. This disruption results in the plant's premature death, hence the name Sudden Death Syndrome.

Depending on the disease severity and the growth stage at which the plant is infected, SDS can cause significant yield loss. Severe infections can lead to yield losses of 20-70%.

(Image Credit: Daren Mueller, Iowa State University, Bugwood.org)

How to Identify Sudden Death Syndrome

Infection may occur early in the season, but symptoms will not be visible until around the time of flowering. Plants infected with this disease can easily be pulled from the soil. Soybean roots will appear rotted and blue fungus can be found in masses on the main or tap root. The inside of the roots will be gray to reddish brown instead of a healthy white color. If you were to split the main stem lengthwise, the insides would be a discolored grey to brown. However the pith will still be white, which is important to differentiate this disease from brown stem rot.

Foliar symptoms appear after flowering, around the R3 stage, and are identifiable early on as yellow chlorotic spots between the leaf veins. As the disease progresses, these spots merge together and lesions turn necrotic and brown as the tissue dies. Leaves may be curled and eventually detached from the plant. Defoliated plants will still have petioles attached to the stem, which is commonly associated with sudden death syndrome.

Correct identification of SDS is vital as it can mimic other diseases like Brown Stem Rot (BSR). However, unlike BSR, SDS does not cause pith browning. The presence of blue fungal growth on the roots is a strong indicator of SDS.

SDS symptoms typically manifest after flowering. Initial signs include yellow or white spots between the leaf veins. As the disease advances, these spots enlarge and darken, while the veins retain their green hue. In advanced stages, leaves wither and fall, leaving the petioles (leaf stems) attached to the plant.

(Image Credit: Martin Chilvers, Bugwood.org)

Geographic Impact of Sudden Death Syndrome

SDS is widespread in numerous soybean-growing regions globally. In the United States, it is prevalent in the Midwest and the South, although it has been reported in other soybean-producing states.

High-yield environments with fertile, moist soils often harbor SDS. The disease severity escalates in compacted or water-saturated soils.

Timing of Sudden Death Syndrome

SDS typically manifests in the mid to late growing season, particularly during the plant's reproductive stages. However, infection occurs early in the season, soon after planting, with symptoms becoming visible later.

Early planting in cool, wet conditions heightens the risk of SDS.

Lifecycle and Distribution

Sudden death syndrome is a disease caused by a fungus (Fusarium virguliforme) that primarily affects soybeans. This disease is a major cause of yield loss and can be found throughout the United States where soybeans are grown. The fungus infects the roots of the soybean and produces a toxin that moves into the leaves of the plant. This fungal pathogen overwinters in the soil and plant residues.

Initial infection is thought to occur early in the growing season, within weeks after planting. Infection and disease development is enhanced by cool, wet soil and temperatures below 60°F; however greenhouse research has shown the infection can occur at temperatures up to 82°F.

Heavy rainfall and moderate temperatures around flowering promote symptoms appearing on the foliage. Hot, dry weather may delay disease development. However, depending on the stage of infection prior to the dry conditions, the disease may still be severe. The occurrence of sudden death syndrome is greatly influenced by weather conditions--if conditions are not favorable, then the disease will not develop.

How to Manage Sudden Death Syndrome in Soybeans

Research has shown that sudden death syndrome can result in approximately 50% yield loss in soybean. Early planting into favorable conditions can often increase likelihood of disease development. A cultural approach would be to avoid early planting in fields that have a history of the disease, but not so late as to decrease yield potential.

Soybean seeds with moderate to high levels of resistance are available. Crop rotation can also reduce the severity of sudden death syndrome. Other management practices, such as improving drainage or reducing compaction can also help avoid this disease. Currently there are no foliar chemical applications that prevent or treat sudden death syndrome. Research is being conducted on seed treatments to determine the amount of control provided against sudden death syndrome.

Effective management of SDS begins with purchasing partially resistant seeds.

For example, FBN® offers a 2.1 relative maturity Enlist E3® traited soybean, PL2E211, with a score of 7 out of 9 for Sudden Death Syndrome tolerance.

Soybean seed treatments containing fluopyram are also effective.

Learn More About Sudden Death Syndrome in Soybeans

Disclaimer

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