Recovery and Pathogenicity of Rhizoctonia solani and Binucleate Rhizoctonia-like Fungi in Forest Nurseries

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Abstract
A baiting technique using slash pine stem segments provided a rapid, sensitive, and accurate means of assessing inoculum potential of populations of Rhizoctonia solani and binucleate Rhizoctonia-like fungi (BRLF) in forest nursery soils. Recovery of R. solani and BRLF from soils was best when stem segments were from 45- to 75-day-old seedlings and when soil plates with stem segments were incubated for 48 hr at 20-30 C. Percentage of stem segments colonized was highly correlated (r .gtoreq. 0.95) with population density detected by the multiple-pellet soil sampler method. However, the stem segment method was more sensitive for detecting small populations of R. solani and BRLF in the forest nursery soil. In an inoculum density experiment, the number of segments colonized in the stem segment assay was highly correlated (r .gtoreq. 0.85) with damping-off severity. However, not all isolates that colonized stem segments were pathogenic to slash pine seedlings.