Persistent cool and wet weather across Ohio has created ideal conditions for soybean seedling diseases. As we move through the early stages of the growing season, it’s critical to scout fields for symptoms and signs of seedling blights and root rots that can compromise stand establishment and yield potential.
What to Look For
Soybean seedling diseases are often difficult to diagnose in the field because symptoms can overlap with abiotic stress or insect injury. However, early identification is key to managing these issues effectively. Here are some common culprits to watch for:
- Pythium seedling blight: Look for water-soaked, mushy seedlings with poorly developed roots. This disease thrives in cool, saturated soils.
- Phytophthora root rot: Symptoms include mushy stems and stunted or wilted seedlings. Unlike Pythium, Phytophthora prefers warmer soils but still benefits from wet conditions.
- Fusarium root rot: Characterized by light to dark brown lesions on roots and a reduced root system.
- Rhizoctonia seedling blight: Look for dry, sunken, reddish-brown lesions on the hypocotyl.
For accurate diagnosis, collect about 10 symptomatic seedlings from different areas of the field, keeping the roots intact. Gently remove excess soil, wrap roots in damp paper towels, place in a sealed plastic bag, and ship promptly to a diagnostic lab. For guidance on where to send samples, see our previous article on diagnostic submission here.
Seed Treatments: Not a Silver Bullet
Even with seed treatments, seedling diseases can still occur. The Crop Protection Network (CPN) publication Seed Treatments: Questions that Emerge When Plants Don’t outlines several reasons why treatments may fail:
- The wrong active ingredient for the pathogen present.
- Suboptimal application rates.
- Environmental conditions overwhelming the protection.
- Misdiagnosis of the actual cause of poor emergence.
Choosing the right fungicide seed treatment is essential. For example, metalaxyl and mefenoxam are effective against Pythium and Phytophthora, but not against Fusarium or Rhizoctonia. Refer to the updated 2025 Fungicide Efficacy Table for guidance on active ingredient performance.
Scouting Resources
The Crop Protection Network offers excellent resources to support your scouting efforts:
- Scouting for Soybean Seedling Diseases
- Overview of Soybean Seedling Diseases
- Fungicide Efficacy for Control of Soybean Seedling Diseases (2025)
Help Us Improve Disease Management – Take the Survey
We’re collaborating with the Crop Protection Network (CPN) to better understand how seedling diseases are impacting soybean production across the region. Our goal is to support professionals in making informed decisions on soybean disease management.
To help us improve the effectiveness and value of the information we provide, we invite you to participate in the 2025 Soybean Seedling and Stem Disease Survey. Your input is very valuable to us.
- Participation is voluntary.
- You may skip any question or exit the survey at any time.
- The survey is anonymous—no names, IP addresses, email addresses, or any other identifiable information will be collected.
- You must be 18 years of age or older to participate.
Please take a few minutes to complete this short survey:
Take the CPN Soybean Seedling Disease Survey
Your input will help shape future research and extension efforts.