Used roundup on a 20 metre high ghost gum planted on the council medium strip. The roots were cracking the path on the front of the house and the front verandah.
Took about 3 months before the tree was fully dead.
The arborists the council hired to cut the tree down said it looked like boarers got into the tree as there were holes all around the lower trunk. All up they had it cut down to a stump in about an hour, great to watch.
Pretty sure they report back to the council on what they think killed the tree. After repeated requests for the council to remove it because it was damaging the footpath and my home, I took matters into my own hands and gave the tree a good drink.
Didn't cost me a cent. Ghost gums are filthy trees. They drop leaves all year round, branches, nuts, it never ends.