Rhizoctonia solani (belly rot)

For other uses, see Rhizoctonia solani (disambiguation).

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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

Belly rot is caused by the soilborne fungus Rhizoctonia solani, and can be a serious problem on cucumbers grown for pickling. The disease is most damaging to cucumber, but the pathogen can attack all cucurbits to some degree. R. solani is a very common soil inhabitant and invades cucumbers in contact with soil. The disease can occur over a range of temperatures (46 to 95ºF), but is most damaging near 80ºF. Temperature is more important than moisture for disease development, but high humidity and excessive moisture favor infection. The belly rot pathogen can be disseminated within and among fields by moving soil and infected plant parts by equipment and irrigation water. R. solani survives in the soil as dormant mycelium and in infested crop debris as dormant sclerotia. It is also a pathogen of many weeds and other crops, but only certain strains of the fungus (AG-4) can attack cucumber.

Symptoms and Signs

Belly rot symptoms occur on the underside and blossom end of cucumber fruit, producing water-soaked, tan to brown lesions. As the disease progresses lesions become sunken, cratered, irregular in shape, and dried. Infected fruits are firm and a soft rot seldom occurs. Belly rot reduces the quality and marketable yield of cucumbers.

Management Approaches

Biological Control

No biological control practices have been developed for belly rot.

Cultural Control

Practice a three-year or longer crop rotation between cucurbit crops. The belly rot pathogen can attack many weeds; thorough weed control is essential for crop rotation to be most effective. Crop debris should be promptly and thoroughly incorporated after harvest to hasten the breakdown of the pathogen’s dormant resting structures. Belly rot can be controlled effectively by not letting fruit touch the soil. Plastic mulches are often effective in preventing belly rot in semi-arid and arid production regions.

Chemical Control

Soil-applied fungicides provide inconsistent disease control. Soil fumigation can be effective in certain regions.