Egg masses on tree trunks
The egg case looks like gypsy moth. This time of year is consistent with when gypsy moth eggs are laid. I advise scraping this egg case off the tree https://cdn.shopify.com/s/files/1/0145/8808/4272/files/FR-171A.pdf. Otherwise, they will remain on the tree throughout winter and hatch around April. There are also pupae (white and black things) towards the bottom and lower right in the photos. This is less common for both of these life stages to be present together.
I was afraid you would say that. There is a pretty heavy infestation along 6 mile east of Farmington in Livonia.
These are Wayne county trees, should they be alerted?
I recommend you contact the municipality where the egg cases were found. The Department of Public Works would be a place to start. The last year has had an increase in gypsy moth outbreaks, and it is useful for the local communities to know which areas and resources are susceptible to damage.