A disease of Jeffrey pines (Pinus jeffreyi Grev. and Balf.) at Lake Tahoe Basin, California, caused by Elytrodenna disease (Elytroderma deformans) was studied for 7 years after a severe outbreak of the fungus in 1971. Among 607 Jeffrey pines on six plots, about one-half were heavily infected and about one-half were moderately or lightly infected in 1971. No uninfected trees were observed. During the 7-year study, about one-half of the trees remained unchanged in vigor, disease intensity, or both, and about one-half decreased in vigor, became more heavily infected, or both. Of the original 607 trees studied, nearly one-third died before 1978. Average radial growth of surviving trees was less per year after the outbreak than before, and heavily infected trees were growing more slowly than lightly infected trees. Intensity of the disease, however, was not related to stand basal area.

Little is known about Elytrodema disease (Elytroderma deformans [Weir] Darker) in seedlings or very young trees. Of 100, 2-0 Jeffrey pine (Pinu jeffreyi Grev. & Balf.) seedlings planted in the Taylor Creek area of South Lake Tahoe, about half survived from 1973 to 1987. During this period about two thirds of the surviving seedlings became infected with Elytroderma disease. Of the trees that died, only three were infected with the disease, and none was infected before 1981-82. Earliest infection of surviving seedlings was in 1976, with 1980-81 the only interval without infection. More than half of the infected trees were infected in the terminal shoot, indicating future impact on survival and height growth. No significant growth effects were measured between infected and noninfected trees in this study, however. On sites with high disease hazard at Lake Tahoe, avoid planting Jeffrey pines. Regenerate with resistant conifer species.