Very tall tree at cottage. N. of Belleville on Crowe Lake. Effected side faces n.w. Pic. attached. Top of tree looks healthy. Tree a fair distance from the lake itself. Not too far from gray water pit, but we’re very organic in that respect.
It is not a surprise that the tree you are inquiring about is a maple. Thin barked trees such as sugar maples, fruit trees, beech and honey locust to name a few, are susceptible to splits and fissures. Cracks and splits in tree trunks are actually not uncommon and are usually not a major threat to the tree.
According to the Missouri Botanical Gardens, cracks and splits most often occur due to cold temperatures. These frost cracks occur when the inner and outer wood in the tree’s trunk expands and contracts at different rates when the temperature changes. They often originate at a point in the trunk where the tree has been injured in the past and most often occur in maples.
While there is not much you can do for a crack like the one you have shown in your photo, what I would suggest is giving the tree the best conditions to continue growing healthily. Top dressing the base of the tree with compost and providing it with water during drought periods would be beneficial. There is no need to paint or fill the crack, just keep an eye on it and promote good growth for your maple.