Susceptibility of ponderosa pine to western gall rust within the middle Columbia River system /

Ponderosa pine from the middle Columbia River system proved to be highly resistant to western gall rust. Only 28 percent of the seedlings that were inoculated at the beginning of their second growth year were infected 39 months after artificial inoculation. Three major resistant reactions were observed: trees that expressed no symptoms, trees that had visible bark reactions, and trees in which the fungus causing the initial infection later died.

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