for your reply. In light of your comment, I have to say that in looking at the leaves again, I'm not sure now that they are ash. You could be right about hickory, (we only get bitternut hickory in this area) and I'll try to get a better ID by showing the larger photo to someone who knows trees.

Leaves of ashes and hickories do look a lot alike: both are pinnately compound and have serrate-margined leaflets (to different degrees). A good way to separate them is to determine whether the leaves are attached to the twig in an alternate (hickory) or opposite (ash) arrangement. In turn, this would require a zoomed-out view to see whole leaves (instead of zoomed-in on leaflets).

Feel free to upload host plant photos; we just delete them once the ID is confirmed. The serration on the leaflet margins looks more like hickory to me, and the galls look more like hickory Phylloxera galls than like anything I've seen on ash (Dasineura pellex is the closest ash gall I know of to this). I was thinking the narrow leaflets were suggestive of bitternut hickory.

of the leaflet. I am not sure this will help, but now that I look at this larger version of the leaflet, I am inclined to agree, not an ash, probably a hickory. Hope this photo helps somewhat.