3-mm gall on upper surface of Q. lobata leaf. Having trouble finding a match in the Russo field guide that occurs on white oaks.
Host tree observed here: https://www.inaturalist.org/observations/182831107
Host tree observed here: https://www.inaturalist.org/observations/182831107
On Quercus sp., I think Q. douglasii?
On Blue oak, Quercus douglasii
On dorsal side of Q. douglasii leaves.
Host tree observed here: https://www.inaturalist.org/observations/182831107
On blue oak