Where do you live? What is your watering regimen (frequency and duration)? Can you take a picture of the edge of the remaining grass from a distance of 3 inches? I need to see the blades of green grass and blades of any yellowing/browning grass up very close. You're getting plenty of light. St Aug grows very well in full shade as long as it gets light from somewhere. For example it will grow poorly under the low canopy of a magnolia tree but it will grow fine under the canopy of any tree with bottom limbs 6 feet high or more.

I'll see if I can strike through all the information in that last message that might apply in Canada but does not pertain to Florida turf. The information you have received has been good but I have to tell you a bit more. Going from a chemical dependent lawn to a healthy organic lawn takes time and work. But it is worth it. The chemicals and pesticides have killed the microbile life in the soil. It takes time to fix this. After looking at your lawn, I see your excess watering has created mold. Use a hard rake and rake everything off the dirt.Before you seed or sod go to a Organic shop and get some products and apply as directed. I would use some liquid seaweed, alfalfa and OM Booster. Don't use corn gluten if you are using seed as it stops seed germination. If using sod, don't let it dry out for the first week. But don't drown it either. Then water once a week, in the early morning for about 1 hour. Fertilize every 5 to 6 weeks with a quality fertilizer. Make sure NO urea or sewage or manure in fertilizer.I have a friend doing Organic in TN. If you need to know which products to use in the USA I can find out for you. Mow the lawn on a routine. Once every 7 days in the early morning or evening, never during the hot part of the day. Don't cut it short, never less than a 1.5 inches for the type of grass you are using. We use Kentucky bluegrass up here and it should be 2.5 inches long. Never cut more than 1/3 of the lenghth when you cut or the lawn may go into shock. When going from a chemical lawn to Organic, you won't see the best results until the 3rd year. The 1st year can look bad and the 2nd will be ok. But the 3rd should look great.Check out my web site www.globalorganicsolutions.ca and email me about anything and I will be glad to help you. If you use sod and after its been down for a couple days take a light roller and roll it to get the roots in contact with the soil.If you can do a soil test, its good to know the Ph. But you need to rake out all the moss and loose grass.I would take it back to bare soil.Good Luck Most of it does not apply because you won't be seeding. Most of the rest does not apply because you don't have mold. He almost got the part about the roller correct. Rolling needs to be done no later than immediately when you apply the sod, if you are going to apply sod. With St Aug you really don't have to unless you want to change the variety. When I converted from chemical to organic, it looked incredibly good in 3 weeks. It has never looked poorly since. My soil is mostly sand fill that I had brought in, so it is a lot like what you will encounter. I suppose it is possible it might take longer to see great results but I would start looking immediately.

Have you talked with the people at your county office of the University of Minnesota cooperative Extension Service about this? Since the onset apparently was fairly sudden I would suspect a plant poison. That grass as well as plants were involved points to that as well. Testing would confirm that but may be fairly expensive. Here is a link that might be useful: UM CES

most grasses are full sun ... and what tree is above.. some of the maple clan.. among others.. simply suck the life out of plants under ... are we to presume these are garden grasses.. rather than lawn plugs??? where are you.. and are they zone appropriate.. could winter have set them back??? ken