Soybean Root and Stem Diseases: Scouting and Management

Seedling diseases like Pythium, Fusarium and Rhizoctonia root rot in soybeans accounted for over 16 million bushels in yield loss in 2025.¹

But once you’re past the seedling stage, more dangers lurk. Each year U.S. soybean growers lose millions of bushels of yield due to soybean root diseases. Preventing yield loss starts with knowing how to identify and manage these diseases. The following soybean root and stem diseases are critical to monitor.

Soybean cyst nematode

(BASF internal photo)

Soybean cyst nematode (SCN) is the single most economically destructive pathogen for soybeans, responsible for more than 70 million bushels of yield losses in 2025.²

SCN can infest fields with all types of soil and environmental conditions but especially thrive in drier conditions and lighter, sandier soil with high pH.

Identifying soybean cyst nematode

Severe SCN symptoms, yellowing or stunting, can appear above ground, but it can cause yield losses of 30% or more before symptoms are visible.³

Scouting roots for SCN females is the best approach. There are two ways to scout, depending on timing:

1. Six weeks after planting: Dig (don’t pull) roots and look for female nodules.
2. After fall harvest: Have soil samples tested for SCN.
   

Managing soybean cyst nematode

SCN can’t be completely eradicated, but crop rotation, choosing seed varieties for their genetic resistance, applying seed treatments and managing soil health can help manage SCN.

Soybean sudden death syndrome

(Duane Rathmann)

Soybean sudden death syndrome caused more than 49 million bushels in yield loss in 2025.⁴

SDS can live for several years in soil or crop residue and develops in compacted soil with cool, wet weather. SDS severity increases where soybean cyst nematode (SCN) is also present.

Identifying and scouting for soybean sudden death syndrome

Foliar symptoms of SDS typically show up after flowering (R1–R2), often in late July or early August.

Identifying SDS symptoms includes looking for:

• Yellow spots scattered between leaf veins that turn into larger brown blotches that may fall out, leaving large holes in the leaves. Eventually, dead leaves will fall from the plant, but petioles remain, attached to the stem.
• Aborted pods (typically in R3–R5)
• Plants that are easily pulled from the soil
• Blue tinge on roots (fungal growth)
  

  

  (Duane Rathmann)

• Symptoms appearing first at field entry points in compacted soil
• Gray or reddish brown internal tissue on main root. In SDS, the pith of the stem will remain white. Brown pith and leaf symptoms may also be brown stem rot, not SDS, so beware.
  

Managing soybean sudden death syndrome

Managing SDS and protecting yields requires an integrated approach employing drainage improvements, resistant varieties, seed treatment and proper planting timing.

Soybean White mold

(Duane Rathmann)

Soybean White mold caused 17.7 million bushels of lost yield in 2025.⁵ White mold spreads best in temperatures between 60 and 70 F. Cooler temps and saturated soil provide ideal conditions White mold. Additionally, planting soybeans less than 30" apart can increase the risk of White mold.

Identifying and scouting for soybean White mold

White mold typically infects soybeans at the R1–R3 growth stages.

• Fuzzy white fungal growth and decimated plant
• Water stained lesions on main stem
• Mature soybean White mold then forms new sclerotia, a blackened protective coating that contains the next wave of White mold infection.

If you’re seeing obvious signs of White mold infection (wilting leaves at the top of the plant), you’ve likely passed the point for effective management strategies. Scout for soybean White mold before R2, checking for saturated soil and areas with particularly thick canopies.

Managing soybean White mold

Controlling soybean White mold involves strategies like applying foliar fungicide at the right time, making row spacing adjustments and rotating non-host crops in fields with a history of White mold. White mold also harbors in many broadleaf weeds, so controlling weeds with herbicides and other management practices can also control White mold. Avoid spreading White mold to uninfected fields by harvesting the infected field last.

Experts are available to help you manage soybean root diseases and differentiate them from foliar diseases. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.

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Endnotes

1. “Soybean Disease Loss Estimates from the United States and Ontario, Canada — 2025.” Crop Protection Network, 6 Mar. 2026, cropprotectionnetwork.org/publications/soybean-disease-loss-estimates-from-the-united-states-and-ontario-canada-2025. Accessed 22 June 2026.
2. “Soybean Disease Loss Estimates…” Crop Protection Network.
3. Lopez-Nicora, Horacio. “Protect Your Yield Potential: It’s Never Too Late to Test for SCN.” Agronomic Crops Network, Ohio State University Extension, 2023, agcrops.osu.edu/newsletter/corn-newsletter/2023-41/protect-your-yield-potential-it%E2%80%99s-never-too-late-test-scn. Accessed 22 June 2026.
4. “Soybean Disease Loss Estimates…” Crop Protection Network.
5. “Soybean Disease Loss Estimates…” Crop Protection Network.