HPIPM:Potato Rhizoctonia Stem Canker

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

Rhizoctonia stem canker 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. Soil-borne and seed-borne inoculum can both be important in the development of Rhizoctonia stem canker.

Plant Response and Damage

Disease symptoms associated with Rhizoctonia stem canker include reddish brown to black, sunken lesions that form on sprouts, stolons, and roots. Large lesions may girdle the stem and kill the sprout. Infected plants may appear stunted and chlorotic. Leaf rolling, purple pigmentation of leaves, and aerial tuber formation are also common foliar symptoms of Rhizoctonia stem canker. The disease delays emergence, reduces stands, and weakens plants, resulting in reduced tuber yield and grade. R. solani can also attack tubers, causing black scurf.

Biological Control

No biological control practices have been developed for Rhizoctonia stem canker.

Cultural Control

Plant high quality seed free from the Rhizoctonia stem canker 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. Crop rotations of at least 2 years between potatoes will reduce soil-borne inoculum, but longer rotations may be necessary in cool, wet production areas. Potato varieties vary somewhat in their reaction to Rhizoctonia stem canker; 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.