" writes:

How do you kill a pine tree short of cutting it down? (It is not ours
to cut). So far 5 gallons of gas has not helped.

Poisining the ground like that is a really bad idea.
Now you have your own personal superfund site.

My guess is that the tree will die.
It may take some time.

Do not pour any more gas there.
If you are caught you are liable for the clean up costs.
Do you think you can afford the costs?
Not to mention the fine.