Damping Off

Damping Off - Solution Guide

Damping Off

The pathogens (fungi & molds) responsible for damping off disease survive very well in soil, planting mixes, plant debris, and even on hard, wet surfaces.

Damping-off can affect seeds or seedlings

Responsible pathogens can attack the emerging radicle-killing seeds before germination. They typically affect seedlings by wiping them out seemingly overnight. An entire tray or large patches of dead seedlings may often occur in a tray or grouping with damping-off. Afflicted seedling stems usually look constricted and show brown discoloration at their base near the soil line.

NOTE: It sometimes looks like the plants are wilting, and watering will worsen the damping.

The pathogens that cause damping-off can be introduced into trays, pots, and soils in several ways

  • Pots, cells, trays, tools, and old starting mixes used in previous seasons that have not been properly cleaned can harbor pathogens that lead to damping off, as can dirty work surfaces, tools, or equipment.
  • Spores of Fusarium sp. can be blown in or carried in by insects like fungus gnats or move in via splashing water.
  • Pythium sp. is often introduced through dirty hands, hose ends that have been in contact with the ground, and sprinkler can caps, which can also be host environments for Pythium pathogens.
  • Rhizoctonia fungi can cause pre or postemergence damping off & root rot issues that can affect many vegetable crops. This pathogen thrives on residual plant debris in the soil.

NOTE: The conditions that encourage germination also speed up the damping-off process. As soon as the seedlings emerge, the medium should be dried out, and the seedlings should be placed in a cooler situation. The drying out and cooling of the medium inhibit damping-off.

Minimizing Risks of Damping-Off for Seedlings

  • Keep seeding areas, equipment & surfaces clean. Sterilize all reused pots or trays in water & bleach solution. Clean with a 10% solution of bleach & water. (1-1.5 cups bleach per gallon of water)
  • Always use a new, fresh starting mix or similar sterilized seed starting product like coco coir.
  • Don't reuse mixes. Do not use potting soil, garden soil, or compost in the mix or individually.
  • Clean any tools that are used for planting. Soak tools for 30 minutes in bleach & water solution before use.
  • Use a heat mat under trays/pots or provide consistent bottom heat appropriate for the seeds' sown.
  • Pre-moisten starting mix and keep mix moist but not soggy. Trays and pots must have appropriate drainage.
  • Keep tools, hose ends, and water-wand heads off the floor. Sterilize heads/nozzles periodically.
  • Water seedlings with clean, warm water. Cold water inhibits germination and leaves seedlings susceptible to pathogens.
  • As soon as seeds germinate, remove the plastic dome or cover and put the seedlings in a bright light.
  • Apply fertilizer judiciously & at the proper dilution rate for seedlings. Avoid over-fertilization that leads to excessive growth.
  • Give seedlings 12 to 16 hours of natural, bright light or grow lights with 8 to 12 hours of darkness. The lack of adequate light causes stretching of the hypocotyl, which is more susceptible to damping off.