VIEW ARTICLE

Ecology and Epidemiology

Distribution and Pathogenicity of Fusarium oxysporum in a Forest Nursery Soil. W. J. Bloomberg, Forest Pathologist, Canadian Forestry Service, Department of Environment, Victoria, B.C; Phytopathology 66:1090-1092. Accepted for publication 28 January 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1090.

Diseased roots of Douglas-fir seedlings killed by Fusarium root rot in a nursery the previous growing season were cultured to determine the presence of Fusarium oxysporum, and the pathogenicity of the Fusarium isolates was determined on Douglas-fir seedlings. All root segments yielded the fungus and about 80% of the isolates were pathogenic. Particulate organic matter, consisting mainly of root fragments, sawdust, and unidentified particles, was collected by flotation from soil cores taken from the nursery. Most root fragments were < 2 mm long and the unidentified particles were < 1 mm long. There was no significant difference in the distribution of any of the particle types by depth in soil. Incidence of F. oxysporum in all particle types was variable, but significantly lower than in diseased roots. The incidence of Fusarium was significantly lower in root fragments that were shorter than 4 mm. Sawdust had the lowest incidence of F. oxysporum. Pathogenicity of Fusarium spp. isolates from the unidentified particles was significantly lower than those from roots. Temperature had no significant effect on pathogenicity of F. oxysporum from diseased roots over the range 10-30 C.