Dead spots in lawn

Question: The grass in our back yard started developing dead spots last summer, which grew bigger throughout the season. Now almost covers a third of our back yard (northeast portion). I tried re-seeding some of the spots early on, with limited success; then I re-seeded the larger areas in late summer/early fall with no success. I need help diagnosing the problem, so I know what solution(s) I should pursue. We did have the sprinklers tested/aligned at the beginning of the summer, and the areas are receiving water (cycle is 3x weekly). There is a large ash tree that is shading the area; we trimmed that tree in the fall. The landscaping was installed when the house was built 19 years ago.

responder: An Ask Extension Expert Replied March 20, 2023, 2:08 PM EDT
response: Hi Karen,  Thank you for contacting Ask Extension, From your email it is not clear how this lawn problem looked when it started. I have several questions, if you could please try to answer that will help us give you some answers.  1. How long do the sprinklers run on each cycle? 2. Do you aerate the lawn each season? 3. Do you fertilize? Is so when and with what? 4. What did the first signs of dying look like? 5. Have you trimmed (crown cleaned and pruned) the tree before? If so did that trimming help the grass?  I have attached a fact sheet several fact sheets to help you define more closely some of the problems that may be impacting your turf. One problem may be competition from the ash tree for light, nutrients, and water. Another may be fungus, Ophiosphaerella korrae which causes necrotic ring spot of Kentucy bluegrass. If you could read these articles to determine if either of these articles seem to address the problem, answer the questions above, and get back to us we will be able to give you a better idea of what may be best to do.  I have also attached several articles on good lawn care and renovation as guidelines for good lawns if you are not already doing these things. Looking forward to hearing from you.   Lawn Care - 7.202 - Extension (colostate.edu)  Turf: Growing Turf Under Shaded Conditions | Center for Agriculture, Food, and the Environment at UMass Amherst  https://extension.colostate.edu/topic-areas/yard-garden/necrotic-ring-spot-of-kentucky-bluegrass-2-900  Renovating the Home Lawn - 7.241 - Extension (colostate.edu)

responder: The Question Asker Replied March 22, 2023, 1:28 PM EDT
response: ﻿Thank you for your response. I have reviewed the materials that you sent. Based on what I read, it sounds like our lawn issues are related to shade conditions and competition for water and nutrients from the Ash tree.  Here is additional information you requested:1) 10 minutes2) No; we have not aerated our lawn.3) Yes (usually in the spring and fall). We use Scott’s turfbuilder. We also applied Revive in the Spring of 2022 (this was the first time).4) I believe that part of the lawn was fully filled in last spring. There was a gradual thinning of the grass/increase in dead areas.5) No, we first pruned the Ash tree in November 2022.I look forward to any additional guidance you can provide us.Thank you,Karen RoneySent from my iPadOn Mar 20, 2023, at 12:08 PM, Ask Extension <<personal data hidden>> wrote:﻿

responder: An Ask Extension Expert Replied March 22, 2023, 9:16 PM EDT
response: I believe you are correct. It doesn't appear  that your lawn suffers from a virus or disease.  Hopefully, your lawn will green up this spring as it comes out of winter dormancy.  You might consider aeration early this spring.  Hopefully, you have been watering your lawn during dry periods this winter.  Here is a fact sheet about winter watering: https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/ Then after aerating consider a light application of a 5-10-5 fertilizer.  CMG