When I was in college a man across the hall had lived in an historic mansion with "200 year old" live oaks and a southern magnolia or two planted near it. During a ferocious hurricane the two oaks went over and the magnolia(s) lost all leaves but remained standing. I think the fact that the leaves were blown off the magnolia(s) shows just how incredibly windy it was. That and the notion that the oaks had held up for 200 years prior to this. Of course, a recent development such as a root pathogen might have diminished their anchorage.

if there are no other signs or symptoms or causes of stress showing, it's probably fine. The behavior you describe is not that unusual. But hard to say with any degree of certainty without more information. Where is the hole, exactly? Has the hole healed, or is the tree rotting from within? Is the root flair exposed?

with 50% of the canopy dead.. its dying ... how long it takes.. in tree years.. is unknown ... all dead stuff has to be removed.. and by that time... and cost.. you may as well remove it all .. yes.. its shocking ... welcome to home ownership ... it really doesnt matter why ... but if you want to find out.. you can hire a certified arborist to come and tell you why ... but you will still have to remove all hanging dead stuff... especially if it is overhanging your house .. or your neighbor.. whether you like them or not ... though we had a horrible MI winter.. none of my 20 oaks of various ages were affected ... you might want to ID and save some of the other trees as replacements for this one... dont make the mistake in getting rid of what might be quality trees.. already on the property ... but do get rid of weed trees .... and if your words failed.. as to what you mean by 50% not sprouting.. get us some pix ... ken

Me again, it is hard to say exactly how long as each vine is different, but I guess a couple of weeks. It will look all mushy and dead. If more shows up repeat the process. You could even use the Round-Up for brush, it is stronger. Or use the concentrate and mix it yourself. ;o)(notice the wink) They build my house over poison ivy vines and they kept coming out under the slab too. And this worked. Just make sure the cup stays full and the vine is in the liquid.