Damping-off refers to sudden seedling death following infection by fungi. Damping-off may be preemergent or postemergent, referring to infection before or after the seedling emerges from the soil. Conditions that slow plant development but promote fungal growth enhance damping-off problems. Cool, wet soils are ideal for damping-off fungi. If the seed remains below ground for a long period before germination, damping-off is more likely. Poor quality seed is also more susceptible to infection.
All plants are susceptible to damping-off fungi. Plants wilt and die suddenly. Symptoms include rotted roots, stem lesions, and general seedling wilt. Most problems at this time of year are in vegetable plantings and flower beds where plants are grown from seed. You could also see damping-off problems in turf.
Fungi that cause damping-off are common in the soil. Fungal species that may be involved include Rhizoctonia, Pythium, Fusarium, Phytophthora, Sclerotinia, Sclerotium, Botrytis, and others. Species of Pythium, Sclerotinia, and Phytophthora are common problems of cool, wet soil. Species of Rhizoctonia, Fusarium, and Sclerotium rolfsii may cause damping-off under warmer and drier conditions.
As these diseases could occur in any soil, how do you avoid damping-off problems? First, start with high-quality seed that germinates and emerges quickly. Choose a site that is well drained and without a history of seedling disease problems. Plant when soil temperatures and moisture conditions favor quick germination and emergence. Using raised beds may help improve soil drainage and increase soil temperatures to allow rapid growth. If possible, buy seeds or transplants that are certified as disease free. Many commercially produced seeds are treated with broad-spectrum fungicides, such as captan, to help protect the seed and young seedlings from fungi. This protection lasts for only a week or two after planting. Fungicides are registered for controlling seedling diseases on some vegetable crops. Refer to the 2004 Illinois Agricultural Pest Management Handbook. Many ornamental plants may be treated, as listed by host in the Illinois 2003 Commercial Landscape & Turfgrass Pest Management Handbook and the 2004 Home, Yard, and Garden Pest Guide.
Consult Report on Plant Disease, no. 615, “Damping-off and Root Rots of House Plants and Garden Flowers,” for more information and pictures. This publication is available on the University of Illinois Vista Web site or in Extension offices.