In field survival of Rhizoctonia solani in soil and in diseased sugarbeets.

Persistence of Rhizotonia solani in the field was investigated by ascertaining survival (competitive saprophytic activity) in soil and survival in diseased plants. Except for one instance, low levels of R. solani survived overwinter in artificially and naturally infested soils. In a sandy loam soil, cropped to sugarbeets, inoculum density increased throughout the growing season from low early spring levels to high levels in July and August. In a silty clay soil, cropped to sugarbeets, inoculum density remained low with only a slight increase throughout the growing season. Survival of R. solani in diseased sugarbeets placed on the soil surface was greater than survival in diseased beets buried in soil. Little reduction in percentages of beets yeilding R. SOLANI COLONIES TOOK PLACE FROM November to April in either buried or unburied beets. The major reduction in survival of R. solani in buried beets occurred during the 6-week interval from April to June.