Galls on All Branches:

[Marine5068]

I have two small(maybe 20ft) trees out back at the edge of my woods that have many galls on them.
I think they look like poplars. The galls are only on the tree's branches. Trees don't have many branches and the galls are about from the size of a golf ball up to the size of a small apple.The whole two trees look infected but no spreading to other dislike trees nearby.
Anyone ever see this before?

 

[Urban Forester]

Galls can be formed by aphids, adelgids, flys, mites, wasps and some fungi. These are most likely twiggall flys, fairly common on (weak) poplars.

 

[ATH]

I see it all of the time. For some reason they infect one tree, but not the neighboring tree of the same species. I don't know, but it may have something to do with some aggregation pheromones???

I see it most commonly on bitternut hickory and second most on shingle oak - less common on other species, but it is still out there.