How to Manage Pests
UC Pest Management Guidelines
Sclerotium Root Rot
Pathogen: Sclerotium rolfsii
(Reviewed 11/05, updated 1/10)
In this Guideline:
SYMPTOMS AND SIGNS
Sclerotium root rot or southern root rot can be a very destructive disease of sugarbeet in some areas but is not generally a problem in the Imperial Valley. Symptoms appear as poor top growth with wilting occurring as the taproot is decayed by the fungus. Under high temperatures, plants will eventually wilt permanently. The pathogen is characterized by cottony mycelial growth on the surface of the tap root with small (1-3 mm) spherical sclerotia that are tan to dark tan when mature.
COMMENTS ON THE DISEASE
Sclerotium rolfsii is a soilborne fungus that survives in the soil as sclerotia, and has a host range of over 200 plant species. The disease is favored by moist soil conditions and high temperatures, 77° to 95°F. The fungus is spread through irrigation water and by cultivation equipment. Although the disease has been reported to occur in seedlings, temperatures are not generally conducive to disease development until later in the season. Frequently, S. rolfsii can cause significant disease losses that may occur just prior to harvest, late August to early September.
There are no chemical control methods for managing this disease. Management can be best achieved by reducing inoculum buildup through crop rotation. Suggested crops to include in a rotation are alfalfa, wheat, barley, corn, or susceptible crops that do not require irrigation during warm weather conditions. Do not rotate beets with beans or other highly susceptible crops and avoid frequent irrigations during hot weather. Yield losses can be reduced through application of nitrogenous fertilizers that promote vigorous growth. Additionally, in fields where Sclerotium root rot has been identified, harvest early.
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