I agree with Margaret about leaving the foliage on. I've also heard that those type of killers actually work better in the fall, something about the plant drawing in and storing nutrients for the winter? Of course, that doesn't help you now. And, I'd try using the extended control Roundup. It's not any stronger and doesn't work any faster (some people have that mistaken idea), but it definitely does inhibit new growth. Sort of like mixing Roundup with Preen.
I've never used ammonia, but I've tried using vinegar and salt in an area I have no intention of ever planting anything. It worked for a while, but stuff still grew back.
