Could dead patches in my lawn be caused by blowing too many clippings into the same area?

Question

I mow my lawn but I pay a company to fertilize and treat weeds. The company is telling me I have something called large patch and pythium. They’re telling me it’s going to cost $130 per treatment and about 6 treatments to fix my problem. There’s about 4 dead spots and they’re all right along the sidewalk edge. I typically blow my sidewalks the same direction and all the dead spots are on the end where most of the clippings accumulate after blowing everything off my sidewalks. Is it possible the dead patches are from too much clippings accumulating in one spot? If so how do I fix this? Also if I do nothing will the grass grow back next spring after the whole lawn goes dormant over the winter? These patches are maybe 2 or 3 feet long on the edge of the sidewalk and go into the lawn from the sidewalk about 12 to 18 inches. So they’re not very big.

Answer 1

Large Patch is a disease that affects Southern US lawns in the fall, after temperatures get to 70F or below. It affects warm season grasses: bermudagrass, centipedegrass, seashore paspalum, St. Augustinegrass, and zoysiagrass. I doubt that this is the problem along your sidewalk. See here for more information.

It's possible that your lawn service has confused large patch with brown patch. This is a fungus in the same genus as Large Patch (Rhizoctonia), but affects cool season grasses: bentgrasses, fescues, and ryegrasses. It occurs during hot, dry spells with very warm nights. See here for more information.

Pythium blight is a fungus that affects the same grasses as Brown Patch (which is why I think your lawn service gave you the wrong name), but it is caused by 12 to 14 hours of wet blades for several consecutive nights when night temperatures exceed 65F. See here for more information.

To sum up

• Large Patch is a fungal disease of the southern US that occurs due to cool temperatures in the fall.
• Brown Patch is a fungal disease of the northern US that occurs during hot and dry spells'
• Pythium blight is a fungal disease of the northern US that occurs due to intensively rainy weather when nights are very warm.

None of these three match the other, which leads me to conclude that your lawn service doesn't know that they're talking about.

As to your initial question - now that we know the causes of those diseases, we know that your grass clippings haven't caused your issues. Dead grass along sidewalks is often the fault of someone using RoundUp/glyphosate to remove weeds from the cracks in the sidewalk on a slightly windy day. It can also be caused, in the northern US, by excessive salting of sidewalks during the preceding winter. And no, clippings don't cause thatch, in case you were wondering (see here, about halfway down the page, for the causes).