Curious to know if anyone can illuminate what the following images show. I’ve seen oak galls before but they are usually brown and round. These are oblong and green. I haven’t seen these before. This oak tree is located out by Bald Hill here in Corvallis. Thanks so much for your collective efforts! -Merka
Benton County Oregon
These are also common galls. They and several others found on OR white oak are also caused by wasps.
This one goes by the common name apple gall, for its current color. Will turn tan when mature. Often find them on the ground in late summer, with holes pecked in them by birds (Jays mostly I think) looking for the residents. Here is some general information about galls by Christine Buhl, ODF.
You might find some more specific information on line. But be careful, one OSU link I checked out seemed wrong. Photos were showing what we call we usually call the popper gall. The ones you have seen and referred to I think. Turns out it was from Ohio State University! Showing how widespread they are, but also how common names vary.
Have fun out there.