A total of 45 nondiseased containerized ponderosa pine seedlings from 10 seedlots were sampled at three different times during the growing season for root infection by Fusarium and Trichoderma at the USDA Forest Service Nursery in Coeur d'Alene, Idaho. More than 90 percent of the seedlings had roots infected with Fusarium. Inverse relationships existed between amount of root infection by Fusarium and Trichoderma. Leach pine cells in which seedlings were growing and soil adjacent to roots and on the inner wall surface of containers were also heavily colonized by Fusarium. Fusarium oxysporum was the most commonly encountered species of Fusarium. Despite extensive root colonization by Fusarium, seedling roots lacked lesions and no effects on seedling growth were detected.
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