A cluster of Oregon Ash trees on the north end of the sqebeqsed trail all exhibit these deformed leaves. The symptoms match those described by the Oregon State University’s Extension service: “ash anthracnose”. (anthracnose is a general term for leaf blight caused by fungi; Plagiostoma fraxini is the specific fungus probably involved here.). OSU Extension adds that the appearance of malformed leaves is most “[c]ommon after wet spring weather, especially if rain persists into June”. It is raining again today, June 20th. Be on the look out for brown or black necrotic splotches on these leaves as the summer progresses.
OSU range map for the Oregon Ash shows that we are near the northern extreme of the natural range of this tree:
