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How To Tell If Your Lawn Has Fungus?

July 28, 2016

Those brown areas in your lawn could be caused by a lawn disease (fungus), lawn insects, or hot dry weather.  So how do you figure out if a lawn disease is the problem?

Experts look for brown, black, white or reddish spots on the individual grass blades or circular brown patches of grass where the fungus has spread from the center.  Sometimes lawn fungus problems show up in the same area each year.

There are a range of lawn diseases that show up with warm, humid weather.  These fungus problems are especially active when your night temperatures and humidity do not drop very much from the levels you are experiencing during daytime hours.  You can help your situation by not watering your lawn in the evening as this helps to hold humidity at high levels next to your grass plants for an extended period of time.  Experts will always suggest that if you have to water, it is best to irrigate in the morning.  Lawns located where air movement is restricted by a fence or hedge generally experience more lawn disease problems as compared to more open areas.

You can help strengthen your grass by not under or over-feeding and by mowing at a taller height.  You can also help strengthen your lawn with the newer grass varieties.  Many of the grass seed varieties that are available in the top-of-the line seed blends today, like the Scotts Turf Builder Grass Seed line, have improved resistance to lawn fungus disease built right in compared to the older grass varieties.

Use the photos and descriptions below tell if you have some of the more common lawn disease problems in your lawn.

If you need to protect your grass from lawn fungus, Scotts Lawn Fungus Control is a good “systemic” cure, which means the active ingredient is absorbed into your grass plants to protect them from the inside.  (Other “contact” controls are not as effective because they must stay on the grass blade leaf surface which means you need to spray frequently as you mow).

Brown Patch on Tall Fescue – Circular patches of dead grass are a symptom of several lawn fungus problems such as Brown Patch and Summer Patch show up during periods of warm temperatures and high humidity. Click photo to enlarge

Brown Patch on Tall Fescue – Circular patches of dead grass are a symptom of several lawn fungus problems such as Brown Patch and Summer Patch show up during periods of warm temperatures and high humidity. Click photo to enlarge

Dollar Spot on Kentucky Bluegrass – Individual grass blades have white blotches edged in reddish brown the shape of an hour glass. Other lawn diseases that show spots on grass blades are Rust and Helminthosporium Leaf Spot. Click photo to enlarge

Dollar Spot on Kentucky Bluegrass – Individual grass blades have white blotches edged in reddish brown the shape of an hour glass. Other lawn diseases that show spots on grass blades are Rust and Helminthosporium Leaf Spot. Click photo to enlarge

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12 Comments
  1. Patti E permalink

    I live in Annapolis, MD and I believe I have a lawn disease in some areas. I have used Scitt’s Fungus Control twice and it does not seem to be getting any better. What is my next step? Should I wait until Fall and reseed that area or will it turn green again. It looked amazing in the spring. I’m anxious to get the spots green again.

    • Hi Patti E
      Another thing to consider based on your location is lawn insects. With lawn insects the browning is more general rather than in a pattern and tends to be more concentrated in sunny areas. If you think the problem is still spreading, you might consider putting down Ortho Bug B Gon MAX to stop these insects. If the brown spots are more circular then it is likely a fungus problem, especially if it shows up in the same areas each year when the temps and humidity climb. There are a couple patch type fungus problems in your area (Summer Patch and Necrotic Ring Spot) that Scotts Lawn Fungus Control helps to suppress if applied early, however it does not completely control. Seeding those spots with a blend like Scotts Heat Tolerant Blue may provide some resistance in the long run. Good luck with your lawn and sorry for your problems.

      • Patti E permalink

        It looks like it starts out white and then dead. Do you think it will bounce back in the fall? Should I leave it alone, reseed,fungus control again, or Bug B Gone?

      • Hi Patti E
        If you are not seeing any active spreading of the problem, then I tend to say leave it alone till you can seed this fall. You can check to see if the grass is dead by peeling back brown leaves on an individual grass plant base to see if you see any white or light green at the growing point where grass blades begin growth. If there is no white or light green plant tissue then the grass is dead.

  2. Justin E permalink

    What is the best way to tell if your lawn is experiencing problems from grub worms or a fungus?

    I just moved into the house in June… new build with a new sodded yard. Lawn was beautiful when it finally rooted but now I have large brown spots. I’m thinking it is grub worms but not certain either.

    • Hi Justin E
      If you give me your location I may be able to give you more specific advice. If you have grubs they will be in the root zone where the grass is brown. You may be able to peel the grass back like a carpet because of limited roots. If you have grubs you can treat with a grub killer that gives 24 hour kill. GrubEX is designed to provide prevention when applied in May or June. If you are seeing circular shaped patches this may be a fungus. Scotts Lawn Fungus Control may help. Feeding will help your grass recover.

      • Justin E permalink

        Sorry I should have specified location. I live in Houston, TX. It is St. Augustine grass.

      • Hi Justin E
        The lawn fungus “Brown Patch” is common on St. Augustine grass this time of year. Scotts Lawn Fungus Control will help. If you have fed your lawn within the past month you do not need to feed it now as St. Augustine is starting to slow growth going into the cooler weather. If you have not fed it recently, you could feed with Scotts WinterGuard Lawn Food, however I would not feed past early October.

  3. Justin E permalink

    Do I need to think about bagging when I mow? I usually just mulch.

    • Hi Justin E
      Even though you may have Brown Patch lawn fungus, I do not believe bagging your lawn clippings will reduce the problem significantly. Too much watering, feeding and short mowing can increase the problem, however the main reason Brown Patch shows up this time of year in your area is the shift to cooler temps.

  4. marie dondero permalink

    Hi can you please help,

    I have been using lawn Doctor for 3 years and now have huge brown sections all over my yard. The service person said it was chinch bugs and treated it accordingly but brown spots are still growing. The guy who mows my lawn says it is fungus. Who do I believe? Where can I test the soil?

    • Hi Marie Dondero
      Chinch bugs will primarily attack grass growing in full sun. They like St. Augustine grass and Bluegrass best. The grass will die in large areas and will not generally repair itself after they are killed. Some Fungus will be in circular patterns while others will show spots on the grass blades. Hope this helps you sort out your problem.

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