Isolates of Fusarium oxysporum, F. acuminatum, and F. sambucinum obtained from peat-vermiculite soil mixes were tested for pathogenicity on ponderosa pine, lodgepole pine, western larch, and blue spruce containerized seedlings and on germination of Scots pine and blue spruce seed. Ponderosa pine seedling were the least susceptible to killing by the Fusarium isolates tested. Fusarium acuminatum was the most pathogenic and F. sambucinum the least pathogenic on seedlings. Isolates of F. oxysporum ranged in virulence from very low to moderately high. The only isolate that consistently reduced seed germination was F. acuminatum. Time required for germination was generally not affected by the Fusarium isolate tested. Seedling inoculation techniques allowed for successful differentiation of the pathogenic potential of the Fusarium isolates tested.
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