How do you kill the roots of a very old tree/bush when removing them is not an option?

The tree/bush is an antique quince and the roots shoot up all over. I really need it to be dead. Any ideas.

How do you kill the roots of a very old tree/bush when removing them is not an option?
Concentrated Roundup herbicide will kill it 100% roots and all. :-). Its a contact herbicide that kills any plant it touches and the chemical travels to the roots as well killing the entire plant. Just make sure you don't get it on any plant you don't want to kill. You can get it at any of your local garden stores.
Reply:gasoline it might be expensive but try it it works for bushes just don't light it
Reply:pour bleach on them