(Cronartium ribicola)

Photo 51: USDA Forest Service

Biology

• this is a fungus that attacks several species of pine, especially Eastern White Pine, Western White Pine, Sugar Pine, Whitebark Pine, Limber Pine, and Southwestern White Pine
• the fungus enters the leaves and spreads to the branches
• the disease has a complex life history and cannot spread directly from pine to pine but must develop on an intermediate host: the leaves of Gooseberries or Currants (Ribes spp.)
• the fungus seems to have little impact on Gooseberries or Currants

History in Canada

• introduced on imported pine seedlings from Europe to New York (1906) and to Vancouver (1910)
• slowly spread across North America

Photo 52: USDA Forest Service

Impact on Trees

• seedlings are most vulnerable and usually killed
• older trees can have branches or tops killed by the fungus but will survive as long as the trunk is uninfected
• tree is killed when the infection girdles the trunk

Control

• past efforts involved removing the intermediate host (Gooseberries and Currants) or preventing them from being grown in important pine-growing regions
• preventing the shipping of pine nursery stock from infected to disease-free areas
• pruning lower branches to reduce the likelihood of infection migrating to the trunk
• developing disease-resistant strains for replanting

Links

• Canadian Forest Service, Natural Resources Canada. White Pine Blister Rust. (http://www.pfc.scf.rncan.gc.ca/diseases/ctd/Group/Rust/rust7_e.html)
• Forest Pathology. White Pine Blister Rust. (http://www.forestpathology.org/dis_wpbr.html)
• Wikipedia, the free encyclopedia. (http://en.wikipedia.org/wiki/Cronartium_ribicola)