Investigations of containerized conifer seedling root diseases at the Champion Timberlands Nursery revealed that Fusarium oxysporum was most commonly isolated from seed, seedling roots, and styroblock containers. Amount of seed infection varied widely among the seedlots tested, but was usually below 5 percent. Runningwater rinses did not reduce amounts of Fusarium detected on seed. Douglas-fir and lodgepole pine seedlings with disease symptoms had roots that were much more colonized with Fusarium than seedlings without symptoms. Fusarium inoculum existed within soil mixes and on root fragments within seedling plugs. The inner walls of styroblocks were also extensively colonized with Fusarium, especially at the bottom of the plug. Hot water cleaning and treatment with bleach reduced, but did not eliminate, Fusarium within styroblocks. Sufficient inoculum remained to pose potential threats to subsequent crops of seedlings. Resistance to benomyl was not detected with in vitro tests, although most F. oxysporum isolates displayed some level of resistance to captan, Botran, and Banrot.
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