Maple tree blight
Or neighbors large mature maple trees have been attacked by some type of blight (spots on the trunk and loss of leaf production). This has been noticeable over the last several years. This year one of them is really sparse an will have to come down soon. However, until this year, our trees have been fine. Now I see ours are likely infected too. question: what could it be and can they be saved? Could it just be the end of their life span? (About 50+ years old) Thank you,
The trunk in the photo does not show spotting from disease. There are some light gray-green spots/patches. These are lichen, which is part algae, part fungi. It is harmless to the plant it grows on. It is simply using the plant for support.
However, when a tree has a huge increase in the amount of lichen on the trunk, that can be a symptom (not cause) that the tree has a problem and is decline.
There is no maple blight going around. You do not say what species of maple your neighbor has, but if he has Norway maples, then it is common for them to die at about this age. Usually the cause is girdling roots (roots strangle the tree). Here's more about that: https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/Landscape/HG20...
You can send us close up and wide photos of your tree for diagnosis. Another option is to have a certified arborist look at it. Most are associated with tree service companies. To find one certified (by the International Society of Arboriculture--ISA) near you, go to: treesaregood.org