Distribution, Severity, and Impact of Swiss Needle Cast in Douglas-Fir Christmas Trees in Western Washington and Oregon. E. Michaels, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. G. A. Chastagner, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. Plant Dis. 68:939-942. Accepted for publication 13 July 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-939.

In 1981, 53 plantations of Douglas-fir (Pseudotsuga menziesii) Christmas trees in western Washington and Oregon were surveyed to determine the incidence and severity of Swiss needle cast caused by Phaeocryptopus gaeumannii. Presence of pseudothecia, loss of needles, and associated disease symptoms were tabulated for 50 randomly selected trees in each plantation. Diseased trees were found in 48 plantations, and 84% of all trees examined were diseased. Of these, 16% retained less than two full-year complements of needles and were reduced in commercial grade, indicating a potential grade loss for 600,000 trees within the region. Of the infected trees surveyed, 11% retained only current-year needles and were unmerchantable in 1981. Monetary loss within the region attributable to needle loss is estimated at $3.4 million for 1981.