MASTGAR Diagnostic Case Study

The Question

I need assistance identifying a lawn/grass issue that was presented by a resident of Hennepin county. The resident (8yr property owner) has observed the same grass pattern every year. The grass will become more normal looking by early summer. The lawn is maintained by an association receiving weed killer, fertilizer and regular mowing. Lawn has a sprinkler system. The neighboring lawns do not have this problem. Can anyone identify the disease so that it can be corrected?

The Responses

• That pattern is too regular to be a random natural occurrence. I would dig up one or more of those spots and see what is buried under there or what remnant of some fertilizing delivery system, etc. Something is making those areas warmer sooner so that they green up. Weird!

• Go to this web page. MSU has a great lawn disease site with photos. When you find one that seems to match, click on it and it will bring that up. There are individual tabs for each along with treatment: Diseases, sorted by Name - MSU Turf Diseases.net - Disease identification and information. A resource guide from the Dept. of Crop and Soil Sciences at Michigan State University

• Assuming that the pattern really is in the same place every year, I would check the master valve on the sprinkler system. I think it leaks, allowing extra moisture near each head. Step A is to confirm that the green spots surround the heads. Note that there could also be leaks at joints, due to improper emptying of the system and rupture during freezing.

• Here is another thought and outside the box. I see that this grass is right next to a path of some sort so I am thinking about people walking their dogs even in the winter. Do these circles go beyond what we see in the picture? If not I'm thinking how far a leash will go for a dog. A dog's favorite spots can become greener than the surrounding grass. This happens primarily on grass that hasn't had enough nitrogen from fertilizer. My thought is each circle is a place where a dog urinated and hence it greened up sooner then the other lawn. My guess is the rest of the lawn is lacking the nitrogen and only the circles have the nitrogen to make the green circles. I forgot to add that lil dogs who do their duty on top of snow will be diluted from the snow but yet be enough nitrogen to green up the lawn but not burn the lawn. If I look at the lowest center of the picture I see a lil kind of dog. Could it be a Yorkshire terrier? This location could be their favorite spot during the winter.

• The pattern of those green spots seems too uniform to be linked to dog urine. Dogs pee where other dogs have peed to cover the scent. These scattered spots don’t look like that.

• It could be female dog urine kills grass when there is no snow, I have no idea but I thought this could happen. I live in the metro area on a corner with a sidewalk and a fire hydrant with tons of dogs walking by. I have yet to have any grass burn out next to the sidewalk and/or next to the fire hydrant. Does that mean all the dogs are male? My soil is more clay, which could be part of the factor. Or as a home owner I'm very lucky. Again ...because when we are sent an inquiry with a picture with so many variables - I threw this thought out. I think this could happen since there is more snow that get piled up next to the sidewalk and we have no idea what the soil makeup is, especially the PH etc.).

• These spots are on a geometric pattern. There must be a man-made reason for this. This is a crucial piece of evidence that rules out many of the theories circulating. If the spots are in the same geographical location each year, it must be due to something buried at each spot....like the sprinkler system. If the spots are in different geographical locations each year, but in the same pattern, then it must have to do with something that is different every year...like fertilizer application.

The Solution

The mystery is solved. The homeowner mentioned she has a River Birch fertilized each year and just reviewed the detailed billing. Apparently the fertilizer is applied in this grid pattern. She wasn’t present to observe the application so didn’t know about the grid pattern. Now we know! Thanks to all for your responses.