Ascochyta Lawn Leaf Blight in Carbondale

Asked May 10, 2019, 11:26 AM EDT

I have a client who has a pretty good case of Ascochyta in his lawn. He has big straw colored areas, the grass looks dead, but I know its not. The grass blades have the characteristics of the disease.

The worst of it is on the south side of the house, where there is full exposure and the house probably radiates heat back to the lawn. The disease showed up at least a couple of weeks ago, I think between wet spells. The other factors I know of is that he used to water every day last season, and the worst affected areas are areas that are watered with the rotator popup nozzles. These are the heads that look like spider legs rotating. They deliver water at a very slow rate, so you have to run the zone for around 60 minutes or else you are just watering shallowly and in this case - every day, frequently.

A company that takes care of his trees recommended to him to have the lawn dethatched with a power rake and for them to spray a fungicide after. I have looked at a number of commercial and university extension website, CSU included, and across the board fungicide is not recommended. I really haven't even seen a recommendation towards power raking the thatch. From there the recommendations are a little mixed, but in general:
  • Core aerate - I aerated heavily in both directions.
  • Sharpen mower blades - I recommended this to him.
  • Set the mower high and mow infrequently for now.
  • Low fertilization - already fertilized - but he did use the natural product, Alpha Lawn.
  • Water deeply for 3 days straight, then back to an infrequent, but regular schedule.
  • Give it time - a few weeks - and it will recover.
Are these the recommendations? I know that fungicides are not recommended. Is power raking? I try to avoid that thankless task as much as possible!

Thank you!

Michael Wieczorek

Garfield County Colorado

2 Responses

The recommendations are fine if it is Ascochyta. But the timing and conditions (from looking at Carbondale weather over the past few weeks) aren't consistent with those conditions which incite Ascochyta.

A photo would be helpful (wide angle, of the entire lawn) and then perhaps a closeup of the crown area of the turf.

I have seen a good amount of mite injury on a few lawns this spring - which has been misidentified by some lawn care folks as other problems (Ascochyta, grubs, cranberry girdler). The advice for mites (depending on severity) would be the same as those you made for Ascochyta - except that overseeding would be necessary if the grass was killed (mite injury is often fatal).

Please send a pic or two if you are able? And swipe the turf (press the paper into the turf as you swipe) with a light-colored piece of paper at the border where the green/healthy turf meets the brown grass. If you see a lot of brown or red streaks on the paper, this would confirm mites. Best to do the swipe on a bright, sunny day (afternoon best).


Thank you for the response Tony. I should have took a picture. I drove by the property a few days ago and the grass is coming the back with more green blades coming through the brown patches. I will be in the neighborhood again tomorrow, and I will take another look while I'm there. I will take another close up look at the blades along the edges, and maybe try the paper thing.