Rhizoctonia-Bacterial Root Rot Complex in Sugarbeet

The Rhizoctonia-bacterial root rot complex is a disease problem of concern worldwide in sugarbeet. A series of studies have been conducted which indicate that the complex is initiated by the fungal pathogen, Rhizoctonia solani. However, only about 6% of the root mass is lost to the fungal infection and 68-71% of the root mass is lost to subsequent bacterial rot. The bacterial rot phase of the problem was proven to be initiated by Leuconostoc. Field studies show that if Rhizoctonia root rot is limited then the bacterial rot phase will be limited as well. Until we develop a better understanding of this rot complex, control efforts should target Rhizoctonia, since Leuconostoc is naturally widespread in the environment. Preliminary evidence suggests that sugarbeet cultivars will be resistant to the strains of Rhizoctonia found in Idaho if they contain the FC709-2 source of resistance.