Damping Off

What is Damping Off?

Damping off is a common term used to describe a condition in which seedlings (both pre-emergent and post-emergent) die abruptly due to pathogenic attacks. It is primarily a soil-borne problem and affects a wide range of plants. The condition is most commonly caused by several types of fungi and can be severely detrimental to crops if not managed appropriately.

Almost any plant that grows from a seed is susceptible to damping off. Commonly affected plants include, but aren’t limited to, tomatoes, lettuce, peppers, beans, cucumbers, peas, and various ornamental flower species.

Regions Impacted

Damping off is a global issue. It predominantly affects regions with high humidity and cooler temperatures, as these conditions are favorable for fungal growth. It’s common in greenhouses and indoor planting areas but can affect any area where soil conditions allow for pathogen proliferation.

What are the Symptoms?

Pre-emergent:

• Seeds rot before germinating, or seedlings decay before they break the soil surface.

Post-emergent:

• Seedlings that have emerged from the soil become water-soaked, wilt, and then fall over at the base. The stem at the soil line is often noticeably thin and constricted.
• The affected base of the seedling is brown to black.
• Older plants may display reduced growth, yellowing, and poor root development.
• Areas of planted trays or soil may show patches where seedlings have died, often referred to as “thinning out.”

What Causes Damping Off?

The primary culprits of damping off are fungi, including species from the genera Pythium, Rhizoctonia, and Fusarium. Overly wet soil, poor soil sanitation, high humidity, and low light levels can exacerbate the problem.

Damage and Detection

Damping off can severely affect crop yield as it reduces the number of plants that reach maturity. The sudden death of seedlings is a clear indication, especially if they appear to be pinched at the soil line or if seeds rot without germinating.

How to Control and Prevent Damping Off?

• Sanitize Seed Trays and Pots: Before planting, clean seed trays, pots, and other equipment with a diluted bleach solution to kill any lingering pathogens.
• Use Fresh, Sterilized Soil: Always use a fresh, sterile seed-starting mix. This minimizes the chance of fungal spores being present.
• Avoid Over-Watering: Keep the soil moist but not soggy. Excess water creates an ideal environment for fungal growth.
• Good Air Circulation: Ensure good air movement around seedlings to reduce humidity. A small fan can help if growing seedlings indoors.
• Avoid Crowding: Space seeds or seedlings adequately to prevent overcrowding, ensuring each plant gets proper air circulation.
• Water from Below: Use a tray beneath pots to water seedlings. This prevents water from splashing onto the stems and leaves, which can spread the disease.
• Maintain Optimal Temperature: Using a seedling heat mat can help maintain the ideal temperature for germination and growth, which can reduce the risk of damping off. Pathogens often thrive in cooler soil conditions; thus, using a heat mat maintained at 70-75ºF (21-24ºC) can aid in warding off damping off.
• Proper Soil Drainage: Ensure the seed-starting mix is well-draining and pots have adequate drainage holes.

Implementing these measures can significantly reduce the risk of damping off, ensuring that your seedlings grow strong and healthy.