Forages: Pythium Seed Rot, Damping-Off or Seedling Blight

Excerpt from Agronomy Guide for Field Crops (Chapter 5)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Incidence
2. Appearance
3. Disease Cycle
4. Management Strategies
5. Updates on Forages: Pythium Seed Rot, Damping-Off or Seedling Blight
6. Related links...

Incidence

Pythium seed rot, damping-off or seedling blight is predominantly an early-season fungal disease of alfalfa. Infection of alfalfa plants most often occurs from the time of planting to several weeks after emergence. The fungus is present in most soils in Ontario.

Appearance

Infected seeds may rot, and severely infected seedlings may wilt, collapse and die. Look for wet or watery lesions on the roots and hypocotyl of infected plants. A girdling, pinching or damping-off of the stem, at the soil line, may be seen causing the seedling to fall over and die. The field is often affected by the disease in circular or irregular patches.

Disease Cycle

Pythium seed rot, damping-off or seedling blight is closely related to Phytophthora root rot. Both produce mobile spores that move through the water film between soil particles to locate and subsequently infect alfalfa roots.

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Management Strategies

Refer to OMAFRA Publication 812, Field Crop Protection Guide, for fungicide seed treatment recommendations. Drain excess moisture and avoid compaction. Plant when soil and weather conditions favour rapid emergence and early growth of seedlings. Increase plant populations to compensate for any plant losses. (Order OMAFRA Publication 812, Field Crop Protection Guide)

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Updates on Forages: Pythium Seed Rot, Damping-Off or Seedling Blight

• Field Crop Protection Guide - Publication 812
  • Forage: Pythium Damping-off

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Related links...

• Diseases
• Forages

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