Symptoms: A soil-borne fungal disease that affects seeds and new seedlings, damping off usually refers to the rotting of stem and root tissues at and below the soil surface. In most cases, infected plants will germinate and come up fine, but within a few days they become water-soaked and mushy, fall over at the base, and die. Damping off disease attacks many plants and is common throughout the United States.
Several fungi can cause decay of seeds and seedlings, including species of Rhizoctonia, Fusarium and Phytophthora. However, species of the soil fungus Pythium are most often the culprit. Damping off typically occurs when old seed is planted in cold, wet soil and is further increased by poor soil drainage. High humidity levels, rich potting soils and planting too deeply will also encourage its growth.
Fungal spores live in the soil and are primarily a problem in seed beds. They can be transported on garden tools and in garden soils taken into the house or greenhouse.
Note: Older plants are rarely killed by damping off primarily because the production of secondary stem tissue forms a protective barrier and limits fungal penetration.
Control: There is no cure for plants that already have damping off. However, you can easily prevent the problem by providing good air circulation. A small fan or simply cracking the lid of the germination tray will suffice. The biological fungicide Mycostop may also be used as a seed treatment to prevent seed or soil-borne diseases. Other steps for preventing damping off include the following:
• When starting seeds indoors, use commercial potting soil, or sterilize your own potting soil in an oven.
• Make sure your soil mix is light and fast-draining.
• Plant seedlings so that the soil surface is near the top of the container to insure proper air circulation.
• Sow seeds thinly to prevent over crowding which can lead to humid, moist conditions.
• Watering systems that provide seedlings water from below are preferable to overhead watering.
• Never water past noon so that the soil surface and the plants are dry by dark
• Avoid overwatering seedlings
Tip: AquaShield (formerly Hydroguard) is a liquid compost solution that helps suppress and resist damping off diseases in both soil and hydroponic gardens.
Photo Credit: Department of Crop Sciences, University of Illinois