So my elm tree is a Chinese Elm

[LaydeeBug]

not a Siberian one. It needs to be pruned, but one company told me to prune in the Fall. There seems to be a lot of dead wood in it, but we did have it pruned about 3 years ago. Should I wait?

[Major Nikon]

1. They told you to wait due to Dutch Elm Disease(DED)

DED is caused by a disease carrying beetle that is attracted to freshly pruned branches and they are most active in the summer. Chinese elms are resistant to DED, but still may succumb to it. Best to wait until the Fall if you can.

[JayhawkSD]

2. Yes, wait until LATE fall

After the leaves have turned and the sap is not running. Fresh cuts emit sap when the sap is running, and the sap attracts beetles. Leaves turn color when the sap stops running, so cuts are mostly inert. Don't wait too late, because once the leaves have fallen off it's hard to tell which branches are dead.

[LaydeeBug]

3. There seems to be a hollow, allbeit a small one

and I want to know if there is anything "nice" I can do for my tree about it.