Infection Period of Phaeocryptopus gaeumannii on Douglas-Fir Needles in Western Washington. G. A. Chastagner, Assistant Plant Pathologist, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. R. S. Byther, Extension Plant Pathologist, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. Plant Dis. 67:811-813. Accepted for publication 3 January 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-811.

Swiss needle cast is a major disease of Douglas-fir grown as Christmas trees in western Washington and Oregon. To determine when needles are infected by Phaeocryptopus gaeumannii in western Washington, trees were introduced or removed from a spray program using known effective fungicides. Spray applications were made monthly during a 52-wk period during 1980–1981. Single applications were made weekly from May through July in 1981. Results indicate that needles are infected shortly after budbreak and that single applications of chlorothalonil provide effective disease control if applied during shoot elongation in early spring.