花旗松
Douglas-firs are vulnerable to the two plant pathogens that cause Rhabdocline needlecast, "Rhabdocline pseudotsugae", and "Rhabdocline weirii". "R. weirii" affects only Douglas-fir trees. The pathogen often makes Douglas fir trees unsalable as Christmas trees and affects the Christmas tree farming industry. Douglas firs are also affected by "Phaeocryptopus gaumanni" which causes Swiss needlecast.