We have 3 American Chestnut saplings raised from an extraordinary tree that survived the blight. Yesterday I found these larvae. I raise native plants to support the animals that rely on them... but these guys are voracious, and if they're not themselves at risk, I'd prefer that they not kill my tree. I could maybe move them to another host plant. They move across the surface of the leaf, leaving behind a single crispy layer and tremendous amounts of frass (shown in second photo).