Application . Results of this study indicate Douglas-fir seedlings with low levels of Fusarium infection in their roots will grow and survive as well as non-infected seedlings after outplanting on a forest site .Abstract . Greenhouse-grown Douglas-fir (Pseudotsuga menziesii var . glauca [Beissn.] Franco) seedlings with roots infected with either Fusarium oxysporum Schlect. or Fusarium proliferatum (Matsushima) Nirenberg were outplanted on a forest site in northern Idaho, U .S .A . No resident Fusarium populations were detected in the forest soil . Fusarium persisted the first four years on roots initiated during the greenhouse phase, but occurred sparingly or was absent on roots that grew after outplanting. Height growth was unaffected, and mortality was not often associated with Fusarium . A seasonal pattern of Fusarium activity was observed . Low levels (10-40%) of initial root infection apparently have little adverse effect on outplanting performance of Douglas-fir seedlings .