Diseases
Damping-Off Complex
A seedling disease syndrome caused by several soilborne fungi and oomycetes. It can occur before emergence or after emergence when the stem or root tissues are attacked.
What to look for
- Seedlings that fail to emerge despite viable seed
- Water-soaked or constricted tissue near the media line
- Seedlings that topple after stem weakening
- Root discoloration or decay in propagation media
Important look-alikes
- Mechanical stem injury
- Severe dehydration
- Heat injury
- Seedling collapse from extreme salinity or other abiotic stress
How to confirm
- Inspect stem base and roots closely
- Review moisture, temperature, sanitation, and media history
- Laboratory diagnosis may be needed to identify the causal organism
Management principles
- Remove collapsed seedlings and contaminated debris
- Avoid chronic saturation
- Improve propagation sanitation and air exchange
- Use organism-specific management when the pathogen is confirmed
Prevention
- Use clean propagation equipment and media
- Avoid overwatering
- Provide suitable temperature and oxygen conditions
- Sanitize trays and tools between batches
Visual study guide
- Healthy versus damped-off seedling
- Stem-base lesion close-up
- Pre-emergence versus post-emergence diagram
- Propagation risk-factor map