I sent this photo of to Baldo Villegas a former UCD entomologist and Rosarian. I thought he might be interested because this plant is in the midst of the Historic Rose Garden. I'll have a look at both canes top to bottom tomorrow. Agasphaerops nigra adults emerge in March and April and feed on leaves. I see no sign of that. The damage in Oregon does look exactly the same. The white in my photos is pith.
