Hello,


There is something very strange going on with your lawn. The lines of damage are too straight to be solely a fungal problem. Some of it is a fungal problem, but I don't think that is the major issue. Either something was mis-applied or else you have a soil issue in these areas.

Was something applied to your lawn?

It looks like one of the yellow areas has a lot of compost in the soil. Take small soil samples in the green areas and yellow areas using a hand trowel. Dig down about 4 - 6 inches. Are there differences? Does one have more organic matter? Is one soil wetter? Is there a layer in one and not the other? Do you hit a hard pan in one area but not the other?

These are the things you are looking for.

The other thing I would check for are crane fly larvae. Dig a 6" x 6" piece of sod (4" deep) with a flat shovel and flip over the sod. Sift through the soil and look for European crane fly larvae. Cut the sod in a green area close to one of the yellow areas. Look up European crane fly larvae on the internet to see what they look like. If you have a problem, you should find 5 or more in your sod sample.

Let me know the answers and what you find with your soil.  Once you respond, I will give you a recommendation.

In general, we don't recommend fungicides for lawns because they require repeat applications and 99% of people can't or do not want to apply fungicides to their lawns for various reasons. Also, as we approach spring, your lawn should grow out of almost all fungal problems when the temperatures warm up and the rain decreases.

In terms of reseeding. Wait until mid-April. And apply a fertilizer at 1 lb. of nitrogen per 1,000 sq. ft. imediately before applying the seed.  Make another fertilizer application 30 days later.

Hi Brian,

Hello,


It looks to me like you have a heavy layer of organic material sitting on top of your soil. Did you have something applied over the soil (e.g. compost) before you seeded the lawn? This can have at least three negative consequences. First, it can hold too much water creating a perfect environment for fungal diseases. Second, it creates layers which causes problems with soil drainage. Third, it provides a lot of carbon for microbes in the soil. When the microbes break down the carbon, they need nitrogen, so they take all the available nitrogen and leave nothing for the grass. Grass that is under fertilized gets damaged a lot more from winter fungal diseases.


I would start by applying a soluble nitrogen source (e.g., ammonium sulfate). Ammonium is positively charged ion, so it binds with the negatively charged soil particles and acts like a slow release fertilizer in cold weather. Apply 2 lbs. of nitrogen per 1,000 sq. ft. Ammonium sulfate is sold as either 20-0-0 or 21-0-0. The first number is the nitrogen percentage and second and third numbers are phosphorus and potassium percentages. If you buy the 20-0-0 type, apply 10 lbs. of ammonium sulfate to 1,000 sq. ft (2 lbs of Nitrogen/.20 = 10) and that will give you 2 lbs. of nitrogen per 1,000 sq. ft. If you buy the 21-0-0 type apply 9.5 lbs. per 1,000 sq. ft (2/.21 = 9.5). Most organic fertilizers do not release nitrogen when the soil temperatures are too low (below 45 degrees), although blood meal does have some soluble nitrogen in it.

It is too expensive and time consuming to try and control lawn fungal diseases. The best defense is two fertilizer applications (about 30 days apart) applying 1 lb. of nitrogen per 1,000 sq. ft. per application. If you start in September, you can use an organic fertilizer. Keep in mind that since most organic fertilizers have a low nitrogen percentage, you are going to have to apply a lot of fertilizer to get 1 lb. of nitrogen. For example, if the nitrogen percentage is 6%, you will need to apply (1/.06) 16.7 lbs. of that fertilizer to 1,000 sq. ft. to get 1 lb. of nitrogen per 1,000 sq. ft.


After you fertilize, I would wait 4 weeks to see how your lawn looks. My guess is that it will recover just fine. If it still looks slightly yellow, I would make one more application at 1 lb. of nitrogen per 1,000 sq. ft. However, with as much organic material that you have in your soil, you may have to put twice as much nitrogen down as normal to keep your lawn green because the micobes will keep eating the carbon and taking the nitrogen until all the excess carbon is gone. I would not reseed unless there are bare areas larger than 3 or 4 inches in diameter where the grass has died. If you fertilize your lawn well, it will get much denser and fill in the weak areas less than 3 inches in diameter.


When you mow, leave the clippings on the lawn as they will provide some nitrogen back to the lawn. Mow your lawn at 2 or 2.5 inches. 2 inches is a good height in the summer. In the winter, raise it to 2.5 inches because the soil is usually a little soft and the wheels sink in a little.  Don’t be afraid to mow your lawn in the winter.  We get periods of sunny weather when the soil dries out and it is firm enough to use your lawn mower.  The more often you mow your lawn, the better it will look.  Grass responds to mowing by becoming denser.  And, in general, the lower you mow your lawn (within a grasses tolerance range) the denser it will become.


I hope this helps.  Good Luck.

Hi Brian,

Thanks Sherry,

People make this mistake a lot.  They think their soils are terrible so they bring in a layer of material and it causes problems.  Even topsoil can cause problems if it is layered.  But a thick layer of organic material causes even more problems as you have experienced.  Fortunately, if you keep your lawn well fertilized for 2 or 3 years, the organic material will break down over time, and eventually, you won't have to fertilize so much.

The other thing you could consider is having your lawn core aerified in the spring and fall for a couple years to remove some the organic material.  The aerifiers pull cores from the lawn which, in your case would be organic matter.  Someone would have to pick up the cores and then apply a topdressing of soil to fill the holes.   This would probably be expensive and only be necessary if you did not want to wait 2 or 3 years for the organic material to break down.

Good luck.

Thanks again Brian.  It seems like the landscape company I hired should have known that this layering with compost would cause a problem for the new grass.  This makeover was quite expensive.  It’s my first experience with hiring for a big project in my yard.  

Hi Sherry,

In general, nothing. The soil needs to be fir and smooth. It can have gentle slopes, but it needs to be smooth. Western Oregon soils grow turfgrass just fine. When you add anything on top (i.e., create a layer) it almost always causes some issue, but you often don't recognize it because grass is so tolerant and the problem is small. Even in your case, it just means you have to fertilize more. The problem will work itself out over time.

Everyone thinks they have bad soil for some reason, and they have to amend it. If you want to amend it, fine (although you are likely wasting your money), but if you do, you need to rototill it into the soil so it gets mixed well so as not to create a layer.

Adding compost or topsoil "sounds" like a good idea. And landscape companies think they are doing a good thing when they add a layer of topsoil or compost, but it rarely improves the grass and often causes problems.

In most cases, spraying out your old lawn (or covering it with plastic) and doing a renovation (removing most of the dead grass with a dethatcher and reseeding) works just fine. You only need to rototill if you need to move soil around and regrade the area. Or, if you are not sure what is below ground, you can take a 3/4" sampler and take samples every 5' or so to see if there are any problem areas. If there are, you either have to dig it out and replace it, or try to rototill and mix the good with the bad to dilute the bad.

This is probably more information than you wanted.

Thats all good information Brian, thank you.