Damping Off in Vegetable Seedlings

Damping-off is usually caused by fungi, Rhizoctonia spp. and Fusarium spp., or by the water mold Pythiumspp. It most often attacks small seedlings and quickly kills them, Older plants can get root rot or crown rot.

Symptoms of Damping Off

Some pests such as cutworms will cut the stems off at or below the soil level, so make sure they are not causing your seedlings to fail. Damping off can make seeds rot before they germinate. If the seedlings have already emerged, when they get the disease, the first leaves of the plant and the stem look water-soaked and mushy. The stem looks thin. After that, the stem and leaves turn brown and the seedlings fall over. This usually happens at or just below the soil level. The roots are gone or have pits in them. If you look closely you can see white weblike fuzz on the surface of the soil.

Prevention of Damping Off

The pathogens that cause damping off are present in most soils. If a seed tray gets damping off, it will usually attack all the seedlings in the tray. The following tips will help prevent damping off.

• If possible, start seed indoors in sterilized seed starting medium.
• If you reuse pots, soak them for 30 minutes in bleach water that is 9 parts water and 1 part bleach.
• Wash pots well to remove the bleech before planting.
• Do not water from the top, but place the pots in a shallow tray and fill it with 1 inch of water. The soil will absorb the water without getting the leaves wet.
• Use a germination mat to keep soil temperatures warm.
• Do not transplant into cold, wet soil.
• When direct seeding outdoors, plant when the soil temperature is warm enough to cause rapid seedling growth.
• Keep soil moist, but not soggy.
• Make sure the seedbed drains well.
• Use high quality seed.
• Thin seedlings so there is good air circulation around them.
• Wash hands well before handling seeds or seedlings.
• Sterilize tools in bleach water before using them.
• Remove diseased plants promptly and discard in the trash.
• Use only fully ripe compost (It should smell like good soil and have no identifiable pieces in it).

Treatment of Damping Off

There is no treatment for damping off. Once the plant is infected, it will die. This makes prevention all the more important.

Chemical Control

There are some organic chemicals that can be used to prevent damping off. These are listed by the Organic Materials Review Institute (OMRI). I will not list them here because new ones come out and old ones get delisted or are no longer produced.

Damping off can be very frustrating. While there are organic chemicals that will prevent it, the risk of damping off can be lowered by following some simple prevention tips. Most of these are things good gardeners do anyway,