Sudden Death Syndrome
- Fungal disease caused by Fusarium virguliforme.
- Fungus colonizes only crown and roots of the plant.
- Above-ground symptoms are caused by a toxin produced by the fungus and translocated throughout the plant.
- Cool, moist conditions early in the growing season often result in higher disease incidence.
- Favorable disease conditions may result from early planting, high rainfall and/or low-lying, poorly drained or compacted field areas.
- Infection occurs early in the season, but symptoms usually do not appear until mid-summer.
Identification and Symptoms
- A blue coloration may be found on the outer surface of taproots due to the large number of spores produced.
- These fungal colonies may not appear if the soil is too dry or too wet.
- Splitting the root reveals cortical cells have turned a milky gray-brown color while the inner core, or pith, remains white.
- General discoloration of the outer cortex can extend several nodes into the stem, but its pith also remains white (Figure 6).
- Leaf symptoms first appear as yellow spots (usually on the upper leaves) in a mosaic pattern.
- Yellow spots coalesce to form chlorotic blotches between the leaf veins (Figure 7 and Figure 8).
- Affected leaves twist and curl and fall from plants prematurely.
- Select SDS-resistant varieties.
- Pioneer has developed elite soybean varieties with improved SDS resistance.
- Soybean breeders have selected for genetic resistance in multiple environments with high levels of natural SDS infection.
- Manage soybean cyst nematode (SCN).
- Improve field drainage and reduce compaction.
Figure 6. Split soybean stem on top shows stem symptoms of sudden death syndrome infection. Split stem on bottom is healthy.
Figure 7. Soybean leaf showing symptoms of sudden death syndrome infection. Drying of necrotic areas can cause curling of affected leaves.
Figure 8. Soybean plants infected with sudden death syndrome. Necrotic areas of leaves dry rapidly. Leaves drop from the plant prematurely, but leaf petioles remain firmly attached to the stem.