Acer macrophyllum
"H. occidentale" affects several species of trees including major hosts including Douglas-fir ("Pseudotsuga menziesii"), western hemlock ("Tsuga heterophylla"), and various fir ("Abies") species. Other notable hosts include sitka spruce ("Picea sitchensis") as well as numerous deciduous trees such as red alder ("Alnus rubra"), bigleaf maple ("Acer macrophyllum") and pacific madrone ("Arbutus menziesii"). Ornamental and landscape trees are seldom affected. This contrasts the Eurasian S-type species, "H. parviporum", which has a fairly strict host range of spruce, fir, and larch.