Maple eyespot galls are bright red and yellow spots that appear on the top of the leaf. Even though it does look dangerous for the tree, it rarely affects any growth or causes any damage to the tree. It is very common to see this starting in the early part of May.
To make sure that it is not a fungal disease you can take a light to the suspected leaf and check to see if there is a dark larva in the center or the ring. Even though it looks like a fungal disease, it actually is caused by a midge which is a small fly-like insect.
These spots are caused by the female midge laying eggs at the under surface of the leaves. The maggot hatches quickly and releases a hormone that causes these spots.
You can treat these spots to remove the mites, but you will not be able to fully remove the spots. When the leaves fall off for the year new leaves will form the following spring unaffected by the previous year’s issues.