Elytroderma disease of ponderosa pine in the Pacific Northwest /

The needle cast of Pinus ponderosa caused by Elytroderma deformans is a native disease that intermittently causes severe local damage.The fungus is perennial within the host, where it spreads vegetatively from one twig or branch to another.Even in its vegetative stage the fungus appears unusually sensitive to climatic stresses.Foliage on infected twigs dies early in its second year, and the twigs usually die within a few years.Growth rates are reduced in approximate proportion to extent of crown damage.Uncrowded saplings and poles with healthy leaders can recover eventually from fairly severe infection if they are not attacked by other parasites while weakened.In mature stands, crown damage from extensive killing of twigs and branches is permanent, moderately infected trees become and remain more susceptible to root disease and beetle attack, and heavily infected trees are often killed directly by defoliation.Despite its alarming appearance in outbreak centers, the disease is just another of the many normal hazards to which forests are subject.It does not threaten to exterminate ponderosa pine as a commercial species even on local areas, and usual good management practices should go far towards reducing its future inroads.Contents TPO CUCU OM Mw pes Nee A Gy yrs oso, Goole ey ehievle\Varre Vel s sPoie eden.ee are we ii Occurrence and Persistence of Outbreaks .........