by Paige Thrush, Nancy J. Taylor & Francesca Peduto Hand
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Rhizosphaera needle cast is a foliar disease that occurs worldwide on a diverse range of conifers. The fungal pathogen, Rhizosphaera kalkhoffii, is responsible for needle cast of spruce species. This disease has been detrimental to Christmas tree plantations, especially those in eastern U.S.A., and to spruce trees in nurseries and landscapes outside of their native range. Spruce species vary in their susceptibility to the disease, which greatly reduces the vigor, aesthetic quality and market value of trees. Repeated years of infection may result in tree death.