something weird at Stone Valley

The last time I went hiking with Otis at Stone Valley we noticed (it was hard not to) that something bad had happened to all of the maple trees. Most of their leaves were destroyed in the manner pictured above. Is it some kind of disease? Was it some kind of pest? The forest floor was littered with little circles of maple leaf. Almost as if someone had taken a hole punch to every leaf!

something weird at Stone Valley