I've never heard that Roundup kills fungus.

If no chemical engineers sound in, my understanding is Round-Up will not help the fungus. No doubt the situation is similar to Round-up and me or a frog.... while it will not kill me if I get some on my feet...dont take a bath in it.

Round-up does something with photosynthesis. Green leaves + Round-up = dead plant.

It can also sorta be used on exposed "green" xylem or phylem however u spell them, I am on my cell.

My opinion is that your landscaper wants to get paid for doing all this work for you. Bottom line is there are always pathogenic fungi in your soil, there are many ways to prevent them from affecting your grass, but Round-up isn't one of them. Get a new landscaper.

Just as I thought it won't work.

That landscaper just wants your money to replace entire lawn. Apply fungus control to brown patches. Solve any low spots that collect water to reduce fungus. Don't iorrigate late in the day or early evening. Fungus grows on wet grass blades more easily.

If there is a fungus, then it can be killed. We had what I think was what is referred to as fairy ring fungus. around a long gone tree in our front yard. I went down to Lowes an bought a fungicide, and applied it in several applications over about 13 month. Today I am growing grass in that area.

I don't remember the brand, but as I remember it was in a green bag.