Except, how would you get a flamethrower like that? Everything's overgrown or destroyed. Technology to make such material is destroyed. Stores or storages that would have it are destroyed. Etc. You'd have to find a survivor that can make weapons to get something made. That, or you'd have to be lucky to find material and have the knowledge to make it yourself.
But yes, true, napalm or some such would work if it was still obtainable. Then, once you've killed a dozen or two of the enemies with it, and are out of fuel, you're stuck with nothing and still a few billion other plants to kill. :P
But yes, true, napalm or some such would work if it was still obtainable. Then, once you've killed a dozen or two of the enemies with it, and are out of fuel, you're stuck with nothing and still a few billion other plants to kill. :P