what is attacking our young tree?
We have a young maple tree not planted by us. It was doing very well in early spring and had happy little leaves starting to form when we left for vacation 2 weeks ago. When we got back we noticed there are spots on the leaves and they're very droopy compared to other maples on the street. There don't appear to be spider mites (did the paper test) but there are some small black bugs under a handful of the leaves. Most leaves have no signs of pests. I did notice an opening in the bark halfway up the trunk and a rather large a split at the base of the trunk. I'm not sure exactly what is attacking our tree, a pest or a disease, so any help would be appreciated. I have attached pictures which will hopefully help. I can take more if necessary.