HPIPM:Potato Black Scurf View Black Scurf

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

Black scurf is caused by certain strains of the fungus Rhizoctonia solani, and occurs wherever potatoes are grown. R. solani has a very broad host range, but the strains that attack potato (mainly AG-3) generally do not attack other hosts. Disease is initiated from soil-borne or seed-borne sources that infect developing sprouts, stolons, and roots. Infection may occur any time during the season, but young tissues are most susceptible and are most severely infected when emergence is delayed in cool soils. The pathogen can survive several years as mycelium or dormant resting structures (sclerotia) in soils, organic matter, and crop debris. Soilborne and seedborne inoculum can both be important in the black scurf development.

Plant Response and Damage

Black scurf appears on tubers as dark brown to black, irregularly-shaped sclerotia on the surface of tubers that resemble soil that will not wash off. Sclerotia range in size from small to large, and may be flat to slightly raised, but do not penetrate the periderm. Black scurf reduces tuber marketability, seed quality, and may also reduce yield. The black scurf pathogen also causes Rhizoctonia stem canker.

Biological Control

No biological control practices have been developed for black scurf.

Cultural Control

Plant high quality seed free from the black scurf pathogen in warm, well prepared soils that promote rapid germination. If soils are cool (below 46ºF), shallow planting (2 inches from the surface) will reduce time to emergence and sprout infection, but not root and stolon infection. Crop rotations of at least 2 years between potatoes will reduce soilborne inoculum, but longer rotations may be necessary in cool, wet production areas. Potato varieties vary somewhat in their reaction to black scurf; highly susceptible varieties should be avoided if possible.

Chemical Control

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.