Violet root rot is a very widespread disease in all areas where beet and carrots are grown and in all soil types. Its control is considered necessary because the fungus continues to grow on the plants after harvest, infecting very quickly neighboring roots and causing significant losses due to rot.
Scientific name: Helicobasidium purpureum, Rhizoctonia violacea
Greek name: Ιώδης σήψη
The disease progresses slowly through the growing season. Symptoms are manifested by foliar wilting. Round spots of affected plants appear in the field, which are visible mainly during periods of drought.
On the surface of the root, more or less extensive violet surface spots are observed, consisting of a network of fine fibers (mycelium), which start from the lower part of the root.
Underneath these spots, tissue decay progresses. In severe infestations the root is completely destroyed.
Pathogen – Growth conditions
Violet root rot disease is caused by the fungus Helicobasidium purpureum, with an imperfect form of Rhizoctonia violaceae. It is a soil fungus and perpetuates itself thanks to special organs, small flattened particles very resistant, called sclerotia. Retention in the soil is ensured for at least 7 years. When conditions are favorable, the fungus grows on the surface and then inside the beet root. It spreads through the soil from one plant to another. The disease progresses slowly and rarely results in the death of the plant. Very often the disease is noticed at harvest. The fungus also affects other plants such as alfalfa, lupin and potato. Poor structure, soil compaction and succession of fungus-susceptible crops are the main conditions that favor the spread of the disease.
Soil disinfectants are recommended, as well as cultural measures aimed at improving soil structure.