Gymnosporangium libocedri (Henn.) F. Kern
Bull. Torrey bot. Club 35: 509. 1908.

Common Names: incense cedar rust; broom rust

• Description

  For descriptions see Kern & PNW Plant Disease Management Handbook.

• Habitat

  Common on incense cedar (Calocedrus decurrens).

• Edibility

  Unknown.

• Comments

  Gymnosporangium libocedri is a rust fungus that infects incense cedar. It forms a witches' broom—a perennial structure in which the branch at the base of the broom is swollen with the growth of many short lateral shoots. In the spring orange, gelatinous spore pustules (telia) appear on infected incense cedar foliage. The teliospores germinate in place, producing basidiospores that are windborne and infect alternate hosts. Alternate hosts include apple, crabapple, hawthorn, mountain ash, pear, quince, and serviceberry.

• References

  Arthur, J.C. & Kern, F.D. (1912). Uredinales: Aecidiaceae (continuatio) and Gymnosporangim. North American Flora 7(3): 161-268.
  Arthur, J.C. (1934). Manual of the Rust of the United States and Canada. Purdue Research Foundation: Lafayette, IN. 438 p.
  Kern, F.D. (1908). Studies in the genus Gymnosporangium. Bulletin of the Torrey Botanical Club. 35:499-511.
  Kern, F.D. (1973). A Revised Taxonomic Account of Gymnosporangium. Pennsylvania State University Press: University Park, PA. 134 p.
  

• Other Descriptions and Photos
  Main Photo
  • Noah Siegel: Gymnosporangium libocedri (CP)
  • Mushroom Observer: Gymnosporangium libocedri (CP)
  • USDA Forest Disease Management Notes: Gymnosporangium libocedri (PDF)
  • PNW Plant Disease Management Handbook: Gymnosporangium libocedri (D & CP) (PDF)
  
  

  (D=Description; I=Illustration; P=Photo; CP=Color Photo)