HPIPM:Damping Off, Seedling Blights Spinach

Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Basidiomycota
Subphylum	Agaricomycotina
Class	Agaricomycetes
Order	Cantharellales
Family	Ceratobasidiaceae
Genus	Rhizoctonia

Scientific Name

Rhizoctonia solani

Scientific Name Synonyms

Moniliopsis aderholdii

Corticium solani

Rhizoctonia napaeae

Thanatephorus cucumeris

Common Name

Rhizoctonia damping-off, blight and rot

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

Many pathogens can cause damping-off and seedling blights of spinach in the High Plains region, including Pythium spp. and Rhizoctonia solani, and perhaps others such as Fusarium solani. 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 saphrophytically on crop residues. Pythium and Rhizoctonia are easily disseminated in irrigation water, contaminated soil on equipment, and movement of infected plant materials.

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 flaccid and die. Seedlings can be killed, but may survive and recover as plants develop.

Biological Control

Deny (Burkholderia cepacia) is registered for protection of roots from Fusarium, Rhizoctonia, and Pythium spp., but its efficacy in the High Plains is unknown.

Cultural Control

Plant high quality seed in warm, well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Avoid excess irrigation and poor drainage. Planting into raised beds can help avoid water logging and promote rapid germination. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in damping off pathogens, but damping-off and seedling blight pathogens have very broad host ranges and can attack most plants.

Chemical Control

Seed treatment with broad-spectrum fungicides is an economical and effective means of reducing disease, but a combination of two or more fungicides is often required to control the spectrum of damping-off and seedling blight pathogens. Chemical controls are most effective when integrated with sound cultural control practices.

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.