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Zion National Park

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Velvet ash (Fraxinus velutina) in Zion Canyon have declined in vigor, and some are dying. This species is aesthetically and ecologically important in the canyon, because it is one of only three tree species that commonly grow to large size on the canyon floor. Ash yellows (AshY), a disease caused by unnamed mycoplasmalike organisms (MLOs), is common in velvet ash in Zion Canyon and was suspected to contribute to the decline of this species. This project deals with the ecology and epidemiology of ash yellows and possibilities for managing velvet ash in Zion National Park.