I just got a few Thuja occidentalis and notice that they have some brown on the inner parts of the leaves/needles. All of it is at the inner part of the plant. There does not seem to be any dying of the leaves. I am not sure if it is simply dirt/dust that has collected over time or if it is some type of fungal/smut type issue?
I can't find any disease that show up as a dust like cover on inner needles.
Picture shows it best on the leaf/branch in the middle of the image.
