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.

It is unfortunate that misinformation continues to be repeated about glyphosate. Denmark has not banned glyphosate, nor have "many European countries". Denmark at one point thought that some of the monitoring they were doing showed that glyphosate could move into agricultural field drainage water in autumn but once they looked at their data and related it to the methodology they used, they enacted no ban whatsoever. As the Danish Environmental Protection Agency specifically stated: http://www.egeis.org/home/main/Evaluation-GlyphosateDEPA.PDF "Against this background, the Danish Environmental Protection Agency believes that no unacceptable risk of pollution of the groundwater is associated with the currently approved agricultural use of glyphosate. The Agency thus does not consider that the updated state of our knowledge provides any technical grounds for the imposition of restrictions on the autumn application of glyphosate." Used properly, glyphosate will not pollute drinking water nor will it have adverse effects on humans. Once applied, it binds tightly to soil particles and is not herbicidally active. If it is applied to hard surfaces such as sidewalks it can move offsite of course. It can also move if there is active soil erosion carrying soil off site. It is of very low toxicity, and breaks down completely into natural constituents over time. It is of equal or lower toxicity than most household products such as detergent, soaps, shampoos, cleaners etc. and far less toxic than some of the "alternatives" often discussed such as bleach, kerosene, high strength vinegars and so on. There is so much misinformation being repeated on the web that it is difficult to get reliable information. This link provides an published overview of the available literature. Regulatory Toxicology and Pharmacology Volume 31, Issue 2, April 2000, Pages 117-165 Safety Evaluation and Risk Assessment of the Herbicide Roundup and Its Active Ingredient, Glyphosate, for Humans http://cat.inist.fr/?aModele=afficheN&cpsidt=1401479

A thick layer of mulch will not stop bermuda grass! I tried to make a flower bed (about 5x15')and my husband used the weed eater to grind the BG down to bare earth. I placed a thick layer of cardboard over that and a thick layer of bark mulch over that. Within a years time the BG was growing through it. I then killed large areas with Round-up and sodded the area. Since my neighbors have BG also, I planted shrubs and trees along the property line and mulched heavily. On the semi-shady side of the lot, the BG hasn't really a problem but on the sunny side I have to manually remove the runners 2-3 x's a year. Generally it grows OVER the mulch, which makes it easy to pull out, but some of the runners grow under the mulch and "pop up" in the garden bed. On those I have to use RU. You really have to stay on top of it. One thing I was concerned about...I was afraid the seeds would blow in from other areas but it's been 4 years and thus far, hasn't been a problem. I don't think a fence will solve your problem however. One thing I've learned about bermuda...it doesn't like shade. By shade I mean trees or shrubs. But mulching alone will not stop it. Concerning weeds...my neighbors make no effort to treat them, as in using a pre-emergent. I don't expect them to, that's their perogative. But you can use a pre-emergent to control most of the weeds in your lawn if applied properly. Also, make sure you overseed your St Augustine yearly. Weed seeds are very opportunistic and will invade areas that are thin or bare. A thick lawn will prevent many of them from taking hold. Good luck!

Ack I just saw this comment but will try and take a picture tomorrow if it's not completely pouring down rain. The St. Augustine (I think?) in the top picture is the dark green grass under the trees and the clumps in the front yard. The bright green grass I think might be Rye growing over the Bermuda which is dormant right now. Oh and we live in Los Angeles.