This is a picture of Callirhytis seminator at the Pickering Creek Audubon Center near Easton, Maryland.
Quercus montana. To met this gall looks like A. pezomachoides, but gallformers says that species is only on Q. alba. Immature A. quercushirta?
On Prunus (cherry)
Total guess on the ID. Hoping someone will correct it
On Populus deltoides
This is a picture of Aceria parulmi on an elm leaf at the Pickering Creek Audubon Center near Easton, Maryland.
On Honey Locust (166024493).
There were quite a few of these, and some were already open and empty. It seemed safe enough to open one. Inside, a small yellow larva (photos 5-6).