Q. Peter: Any idea what’s the matter with my front lawn? Photo’s enclosed. It is about six years old, new sod installed by Blue Sky Nursery, replacing an old lawn. They also went down about a foot/foot and ½ replacing the soil. We had an older gentleman mowing our lawn for several years and continued with his services after the installation but when he retired we changed to Blue Sky who continued to mow and trim for us. Our spraying and fertilizing is done by another company. We are getting too old to mess with lawns or even flower beds anymore but my husband waters the lawn for an hour, two/three times a week during the day hours which is less than last year when he watered every day for an hour. The spots on the photos are on the front lawn and while the older man didn’t rinse off his mower from front to back lawn, those spots weren’t there when he left. Blue Sky uses two different mowers, one for the front and one for our rear lawn (an improving scrub lawn). They maintain the spots, infestation or what ever it is could have been brought in by anyone or anything including small animals, birds or kids etc. They did replace several spaces with new sod three years ago but as you can tell, the spots returned with a vengeance. I took copies of these photos to the Master Gardens @ the WSU cooperative Extension office and they requested I bring a 4” x 2” deep sample of the lawn to them for inspection and maybe they will have a solution to the problem. I plan on doing that this week but would like your opinion. Thanks for any information. M. A. Coty – Tacoma, WA
A. Well my opinion you will receive. First off I wonder what reasoning you were given for replacing the topsoil before putting in a sod lawn. The top foot and a half is was where the most important biological components (bioactive microorganisms) of healthy soil reside. Removing the topsoil is disruptive and an unnecessary expense. It would have been more appropriate to evaluate the existing soil and amendment it for pH, fertility and organic matter. Both fast draining sandy soils and slow draining clay soils can be improved with the addition of organic matter. Furthermore there is a very good chance that the replacement topsoil was of lower quality than the soil that was removed especially when considering the bioactivity of the soil. Second I am glad your husband cut back on watering the lawn since daily watering is unnecessary and detrimental. This watering regime shallow root formation (deep roots are better) and also exacerbate disease problems. Lawns should be watered when the top 2 inches of soil dry out. The frequency and amount depends on the soil type you have but pulling back a small section of sod and looking at the soil is a good idea until you get a sense of how often to water during the dry season. Brining the sample to the extension is a very good idea. The picture you sent me would not be sufficient enough to diagnose a lawn problem. Many lawn have similar patterns- especially from a distance. I suspect it is a type of fungal disease but only with a closer inspection of the leaf blades and soil profile could the exact cause be determine. Once the extension diagnoses the problem then a treatment regimen can be implemented. There is no sure way to pinpoint where a disease came from. Fungal spores can move by wind, on mower blades, on the soles of shoes etc.