I was thinking the same thing. You can't get rid of bermudagrass without killing the St. Augustine. The good news is the St. Augustine stolons grow a half inch a day in the summer. So killing the yard and starting over wouldn't take long. You say the front yard is nearly perfect so in the perfect areas use some of your yard as a nursery and plug the back. The front will recover quickly and the back will soon be looking as good as the front. The key is using the top labeled amount which could range from 3 to 5 ounces per gallon. Then to use it as soon as you can then in about 2 weeks. You should have pretty much wiped out the back lawn. I would then cut the grass as low as possible then plug all you can. Keep it well moist and then wait. I would think by the end of next year you should have a solid back yard. Good luck.

No one asking anyone to read ALL those replies. If you do not want to know what we know, skip our replies. On a new thread or topic, we will come over & reply & you will be back where you are now. jolj(7b/8a) henry, I am going to try solarization on my bahia grass. 90% of the things on this thread will not eradicate bahia grass. This includes round up, which kills the tops, but not the deep roots. Round up will not kill nut sage/ nut grass or common dew berry vines. So I will try this on the bahia. I have heard that the solarization may kill the soil food web, when it kills the weeds. I am planning to sheet compost the beds after I kill the grass/ weeds. I have been told that tilling kills the soil food web. Not sure who is right or if it matters, I give vegetables away every season including the winter. I grow more then I can use, then I must be doing something right. [Like[(https://www.houzz.com/discussions/organic-way-to-get-rid-of-bermuda-grass-dsvw-vd~1521679) I did this in 2011 & it worked great.

Donn, It is Panicum virgatum 'Cloud Nine'. I looked at the exchange page. I didn't even realize that existed until you pointed it out. I need to finish pruning my shrubs before I get around to digging out the grass and figuring out how to get it ready for shipping. I also need to figure out the best timing for this. It looks like you are several planting zones ahead of me. Bella, I like all of my grasses except the Panicum. I have about ten varieties here and there throughout my property and I'm finding that I am unhappy with where we situated the "ornamental grasses garden" and I don't like the way the grasses relate to each other in that area. I am going to move all of them except the Switchgrass. I don't feel like it has enough room in my yard to really show off it's potential. It is also very messy in the late winter which annoys my neighbor to no end. He is extremely fastidious about his yard and can't quite figure out why I have ornamental grasses to begin with. He believes that grass should always be green and mowed twice a week. Not that I'm landscaping for him but since I don't love the plant and it makes him miserable finding bits of it blown into his yard, my removing it can help maintain the peace between us.

No, growth regulators won't kill it.Regularly cutting it down may slow it down. But never allow it to get this tall again. If this is a common nasty weed in your area, several local agencies may have advice, among them Soil & Water; Conservation & Soil District; and your county's Extension Service office. You an locate the latter using this map: http://nifa.usda.gov/partners-and-extension-map