How to Manage Pests
UC Pest Management Guidelines
Rhizoctonia Root and Crown Rot
Pathogen: Rhizoctonia solani
(Reviewed 11/05, updated 11/05)
In this Guideline:
SYMPTOMS AND SIGNS
Aboveground symptoms on older plants include sudden yellowing and wilting of foliage. Leaf petioles die near the crown and wilted leaves collapse and die, forming a dry, brown rosette that persists throughout the growing season. Exposed areas of infected roots are often covered with masses of brown mycelium. The fungus causes a characteristic dry rot that is brown with deep fissures at or near the crown. The root and crown are partially or completely destroyed.
Rhizoctonia solani also attacks sugarbeet in the seedling stage, causing damping-off (see section on Seedling Diseases).
COMMENTS ON THE DISEASE
Rhizoctonia root and crown rot, caused by a soilborne fungus, is a common root disease of sugarbeet. The fungus is widespread, has many crop hosts, and survives on plant debris in soil as small, resting structures called sclerotia. This disease is most common during spring and summer when conditions are warm (77° to 92°F, 25° to 33°C) and soils are moist. The fungus grows through the soil and infects the root and crown of plants. Rhizoctonia occurs in most soil types, but is most severe in heavy, poorly drained soils where water collects.
Check with your farm advisor or field representative on the latest information concerning the availability of resistant varieties in California; if available, use them. Follow good tillage, irrigation, and fertilization practices to promote good crop growth and adequate soil drainage. Plant sugarbeet in rotation with corn or small grains, and when cultivating, avoid throwing dirt into plant crowns.
UC IPM Pest Management Guidelines:
S. Kaffka, Agronomy and Range Science, UC Davis
Acknowledgement for contributions to Diseases:R. T. Lewellen, USDA, Salinas
C. A. Frate, UC Cooperative Extension, Tulare County