Complete Lawn Fungus and Lawn Disease Guide

By TruGreen October 03, 2019
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Why does my lawn have brown or discolored patches of grass?

You put hours into your lawn, doing everything you were told to do to make the grass green and lush. You’ve aerated, fed, watered, and mowed, and everything looked great – until suddenly, it didn’t. Almost overnight, there are patches of dead grass. Or maybe some spots are an unusual color, or just look “off” somehow. Whatever the issue, it’s unsightly, and it looks to be spreading.

Oftentimes, when a lawn develops problems like dead or discolored areas, the culprit is disease or lawn fungus. But before you give up and decide to just replace your lawn with artificial turf, you should know that your grass can be saved. By correctly identifying the problem, and applying the proper treatment, you can eradicate the disease and go back to enjoying a yard full of healthy grass.

How to tell if your lawn has fungus?

The most important step when you spot fungus or another problem on your lawn is to correctly identify the specific type of disease that’s present. Different lawn issues have different causes and symptoms, and treating your grass for the wrong thing could only lead to more damage – not to mention, you’ll still have to deal with the original issues. Before you invest in a treatment, therefore, take the time to closely examine the issue – or better yet, get a professional to identify the disease – so you know exactly what you’re dealing with and choose the right treatment the first time.

There are a number of signs to watch out for that indicate a problem with your lawn, and some of them are more obvious than others. In most cases, discoloration is the most obvious sign, as grass will turn yellow, tan, or brown in spots. Keep in mind, though that it’s not always a disease that can cause this. Higher than normal temperatures, inadequate watering, and insects can also cause dead or dying areas, only underscoring the need for adequate identification.

Assuming that everything else is normal, discoloration is just one sign that your lawn is sick. Brown patches not attributable to pets, slimy patches of grass, a film covering the grass and spots on individual blades of grass are all signs of an issue. While specific fungi and lawn diseases have unique signs, some of the most common types of disease and fungus include:

  • Dollar spot. Usually presents as silver-dollar sized spots of tan or brown grass throughout the lawn.
  • Brown patch lawn disease. Circular shaped areas of brown grass surrounded by a ring of “smoky” colored grass. The area might appear sunken. Usually appears in hot and humid weather.
  • Leaf spot. Infections that present as spots on individual blades of grass. Grass looks gray, tan or brown, but the individual spots on the grass generally look red or purple.
  • Mildew. Appears as a white film over the grass, usually in shady spots.
  • Blight. Different forms of blight affect different types of grass. Depending on the type of blight, it may just kill the grass, or it could present as slimy brown or white patches throughout the lawn.

Again, because some diseases only effect certain types of grass (fusarium blight only attacks bluegrass, for example) it’s vital to know what type of grass you have and the specific type of disease before begging treatment.

How to treat your yard for lawn fungus

Once you have determined what type of fungus or disease is present, it’s time to treat. It’s best to treat a diseased lawn as soon as you spot the problem, as some diseases can spread and kill the whole lawn.

The type of disease or fungus you have will determine the best treatment option. In some cases, the issue is weather or seasonally dependent (such as snow mold, which appears after the snow melts or red thread lawn disease) and will clear up on its own once the weather changes. Other problems need immediate mitigation, such as fairy ring, powdery mildew, or smut, as they can kill the plants or cause permanent damage to the lawn.

To treat your issues, first identify whether it can be eradicated via changing your practices. Powdery mildew, for example, may be able to be taken care of by rinsing the plants and getting rid of leaves or any other nearby debris that is causing it to spread. Avoiding overwatering, letting the grass grow a bit longer between mowing and not over fertilizing can also help clear up the problem.

However, in most cases, you will also need to use an antifungal product to kill the spores and disease on your grass. Choose an antifungal product designed for your type of grass and the fungus it has; otherwise, you risk killing healthy grass as well. A fungicide will not encourage regrowth, and you may need to reseed the diseased area, but it will kill the fungus that’s hurting the grass so that new grass can grow and your other efforts to keep the lawn healthy will be effective.  Keep in mind that in some cases, such as with fairy ring, a fungicide will not work, and you will have to dig up the entire affected area and start over.

Some homeowners prefer to try to treat lawn diseases organically, rather than using fungicide. If your areas of fungus are small, using treatments like neem oil, cornmeal or baking soda solutions can be effective. Before you opt for an organic approach, though, do your research and be aware of the potential drawbacks. In some cases, using home remedies can only make the problem worse, or introduce new, unexpected issues.

Preventing Lawn Disease and Fungus

The best way to deal with lawn disease and fungus is to prevent it from happening in the first place. Often, issues arise due to the way homeowners care for their lawns. Even some well-intentioned habits can cause problems, and making changes can prevent disease or keep it from causing permanent or widespread damage.

Some of the best methods of lawn fungus control to keep disease away include:

  • Watering properly. Overwatering can cause mold, mildew and yard fungus to form. Once your grass is established, water deeply but less frequently. Your grass only needs about an inch of water per week. Water early in the day so grass will dry in the sun; wet grass is more susceptible to fungus.
  • Mow regularly, but don’t cut the blades too short. Grass that is too short is more hospitable to disease. Keep your blades sharp so they cut without damage.
  • Clean up debris from your yard. Leaving piles of leaves, branches and other debris creates the ideal breeding ground for fungus.
  • Improve drainage. If you have low-lying areas or spots that don’t drain well, fix them so that water doesn’t pool and cause problems.
  • Test the soil. Sometimes the problem is due to the nutrient balance in the soil, and changing or adjusting how you feed can solve it.
  • Prevent spread by cleaning tools. Clean all of your lawn tools, including mower blades, rakes and shovels with a mixture of water and bleach to kill any spores that could be hiding there, waiting to cause a problem.

DIY Lawn Fungus Control vs Professional Treatment

If you discover fungus on your lawn, you want to address it right away. But should you DIY it or call a professional for help?

If the issue is a simple fix, and you know exactly what it is and how to go about killing the disease, doing it yourself can save time and money. However, if you don’t choose the correct treatment, you could do more harm than good, and end up spending more in the long run. Not to mention, lawn fungus treatment products designed for consumer use aren’t always as powerful as those used by professionals, so it may take longer to solve the problem on your own.

By hiring a professional, you can be sure that you are treating the right problem, and that the products and treatments being used are the correct ones. It will cost more money, but a lawn care pro can solve the problem faster and prevent further damage to the grass. A professional can also provide insight into the cause of the problem and help you avoid it from happening again. Even if it is a simple fix, working with a professional gives you peace of mind that the issue has been dealt with correct.

Lawn fungus and disease is a common problem, and it doesn’t have to mean that all of your hard work was in vain. Sometimes it’s due to factors out of your control, but taking the right steps to prevent and treat disease can keep your grass looking beautiful all season long.


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