The disease on your beech tree, unfortunately, may be beech leaf disease. This is a very distressing disease of American and European beech trees, particularly as little is known about transmission and thus how it can be prevented.  Current research suggests that it affects the ability of beech trees to photosynthesize and is associated with the nematode, Litylenchus crenatae. There is some disagreement about the additional factors associated with the disease as affected leaves have also been found to carry a fungus and species of bacteria. Some scientists believe that multiple elements need to be present in concert and others that the nematode is able to infect the plant on its own. You can learn more about foliar nematodes in this fact sheet from Missouri Botanical Garden. When you suspect a tree on your property has beech leaf disease, you should have your county's Cooperative Extension test the leaf in their diagnostic lab to confirm the problem.

It is not yet known what the average pace of decline will be for mature beech trees, but small trees can die in less than 5 years. I am sorry to say that there are no effective management strategies yet. Research is underway and some promising experimental treatments are being investigated. This fact sheet from The New York Department of Environmental Conservation is a good synopsis of the current state of investigation and control efforts.

Both iNaturalist and Map Invasives NY are collecting data on areas of infestation which is critical in the effort to learn how the disease is spread and create management tools. You can access the iNaturalist Bust Beech Leaf Disease EcoQuest website here and New York's Map Invasives reporting tool here. You can find a map of reported observations of beech leaf disease from iNaturalist here.

Courtesy of NYBG Plant Information Service