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Abstract
Several diseases affect the growth and survival of ponderosa pine in the Pacific Northwest and serve as agents of disturbance. Probably the most widespread and damaging class of disease agents is dwarf mistletoe, which causes serious growth loss and mortality of ponderosa pine. Dwarf mistletoes (
Arceuthobium spp.) are seed plants that can parasitize all age classes of pine. Decades of research and observation have shown that although dwarf mistletoes spread slowly within and among trees, their localized effects can be quite spectacular. Root diseases caused by the fungi
Armillaria ostoyae (Romagn.) Herink,
Heterobasidion annosum (Fr.:Fr.) Bref., and
Leptographium wageneri var.
ponderosum (Harrington & Cobb) Harrington & Cobb cause localized mortality resulting in gaps in affected forests. Root diseases may spread by root contact, airborne spores, or insect vectors depending on the species of root disease fungi. Stem decays caused principally by
Phellinus pini (Thore.:Fr.) A. Ames and
Fomitopsis officinalis (Villars:Fr.) Bond. & Sing. result in single-tree gaps if trees break as a result of advanced decay. Decay fungi infect wounds on living trees, and decay may take decades to develop to where tree structural integrity is compromised. Stem diseases caused by rust fungi such as
Cronartium comandrae Peck and
C. coleosporiodes Arth. can kill the tops of trees or result in whole-tree mortality. Decayed and cankered trees can serve as habitat for a wide diversity of wildlife. Disturbances in ponderosa pine forests caused by forest diseases can affect forest succession, insect outbreaks, fire frequency and severity, and both animal and plant diversity.
Parent Publication
Citation
Filip, Gregory M. 2005. Diseases as agents of disturbance in ponderosa pine. In: Ritchie, Martin W.; Maguire, Douglas A.; Youngblood, Andrew, tech. coordinators. Proceedings of the Symposium on Ponderosa Pine: Issues, Trends, and Management, 2004 October 18-21, Klamath Falls, OR. Gen. Tech. Rep PSW-GTR-198. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 227-232
