HPIPM:Damping Off and Seedling Blight DB

Author: Howard F. Schwartz, David H. Gent, Gary D. Franc and Robert M. Harveson

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

Identification and Life Cycle

Many pathogens can cause damping-off and seedling blight of dry bean in the High Plains region; primarily Pythium spp., but many other organisms are probably involved in damping-off. Damping-off is associated with cool 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 and pathogenically on alternate hosts and weeds. Damping-off pathogens are easily disseminated in irrigation water, contaminated soil on equipment, and movement of infected plant material.

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. The radicle and cotyledons may become brown and soft after germination, but fails to emerge. Water-soaked, greasy lesions may also form on hypocotyls and roots after plant emergence when infected with Pythium spp., causing the plant to collapse and wilt. Plants can also wilt suddenly; and healthy-appearing plants can suddenly collapse during the heat of the day. After several days, plants permanently wilt. 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. T-22 Planter Box (Trichoderma harzianum strain KRL-AG2) is registered, but cannot by used in alkaline or cold soils. The efficacy of these biological control agents in the High Plains is not known.

Cultural Control

Plant high quality seed in warm (greater than 60°F), well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Avoid excessive irrigation and poor drainage. Planting into raised beds can help avoid water- logging and promote more 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. Conventional tillage tends to reduce damping-off as compared to minimum or no-till operations.

Chemical Control

Seed treatment with broad-spectrum fungicides is an economical and effective means of reducing disease, but is not a substitute for sound cultural 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.