Thanks for your question.

From your pictures, it seems that both ash and beech trees are in this grove. Typically, neither of these two tree species shows the type of gall that is present on the twig you are holding. This leads me to assume that besides possible ash and beech, oaks may also be present. However, I don’t think these are horned oak galls. Horned oak galls typically have spikes protruding from the gall. This is the basis for their name. I don’t see these spikes in the galls shown in the picture where you are holding a twig. For this reason, I’m more inclined to think that these are oak bullet galls attributable to cynipid gall wasps (Disholcaspis quercusglobulus). They are often present on Burr and white oaks. They are quite common in Minnesota. See:

https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/oak/branchesgrowths.html

https://forestrynews.blogs.govdelivery.com/2017/10/27/oak-bullet-gall/

http://minnesotaseasons.com/Insects/oak_rough_bulletgall_wasp.html - :~:text=Oak rough bulletgall wasp is,green bumps on the twig.

https://springfieldmn.blogspot.com/2016/10/oak-bullet-galls.html

Generally these galls can simply be ignored as unless the infection is significantly severe, no damage is done to the tree. See:

https://www.davey.com/insect-disease-resource-center/oak-galls/ - :~:text=Fortunately, galls do not cause,Some leaves may drop prematurely.

https://www.flickr.com/photos/mixedmetaphor/<personal data hidden>/

https://elizahowellnaturewalk.wordpress.com/2021/08/24/oak-bullet-galls-protected-by-hornets/

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