HPIPM:Damping Off and Seedling Blight CC

Author: Howard F. Schwartz and David H. Gent

Taxonomy

Domain	Eukarya
Kingdom	Chromista
Phylum	Oomycota
Class	Oomycetes
Order	Peronosporales
Family	Pythiaceae

Scientific Name

Pythium

Common Name

Pythium diseases

Identification and Life Cycle

Damping-off is caused by a complex of fungi, including Rhizoctonia solani and Pythium spp. Damping-off is associated with cool to warm soil temperatures, excess soil moisture, and delayed seedling emergence. Pathogens associated with damping-off are common soil inhabitants and can survive in soil as dormant oospores or sclerotia, pathogenically on alternate hosts and weeds, and saprophytically on crop residues.

Plant Response and Damage

Damping-off can occur before or after crop emergence. Pre-emergence damping-off results in a brown, gelatinous rotting within the seed coat. Radicles and cotyledons may become brown and soft after germination, but fail to emerge. Water-soaked, greasy lesions may also form on hypocotyls and roots after emergence when infected with Pythium spp., causing plants to collapse and wither. Post-emergence damping-off caused by R. solani begins as elliptically-shaped, brown to black sunken cankers on roots and hypocotyls with a sharp margin between infected and healthy tissue. Plants can become girdled and die, but lightly infected roots often survive and produce nearly normal roots.

Biological Control

Kodiak (Bacillus subtilis strain GBO3) is registered for protection of roots from Pythium and Fusarium spp., but its efficacy in the High Plains is unknown.

Cultural Control

Encourage rapid seed germination and vigorous growth of seedlings by planting high quality seed in warm, well-prepared seedbeds. Avoid planting into cold soils, excessive irrigation, poor drainage, and compaction. Ensure crop residues from the previous crop are thoroughly decomposed before planting. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in damping-off pathogens, but some damping-off and seedling blight pathogens have very broad host ranges and can attack most plants.

Chemical Control

Fungicides are most effective when two different seed treatments are used in combination with cultural control strategies.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.