Treating and Preventing Lawn Fungus

Use this simple strategy to treat and prevent lawn fungus using cultural practices, as well as fungicides when needed. Combining this strategy with a simple lawn care program is the best way to prevent disease from taking over your lawn. 

This simple strategy can be used to treat and prevent almost all types of lawn fungus and disease. For now, don’t be too worried about identifying the different types of fungus since for the most part treatment and prevention options are similar no matter what type of fungus you have. Before using this strategy it’s important to learn what causes fungus and what fungicides should be used, if any, to protect your lawn.  

Also, only use the fungicides outlined in this strategy if you suspect that you have had fungus and disease problems in the past. Eventually the goal is to get you off the need for fungicides. 

Personally, I’ve had to use fungicides in the past but now that my lawn has been strong for several seasons I no longer use them. Instead, I rely on sound cultural practices (more on this below) and a solid lawn care program to keep my lawn healthy and prevent disease from setting in. 

What Causes Lawn Fungus

Of all the lawn ailments, lawn fungus is probably the most confusing and most frustrating. You can be following a pretty strict lawn care program, and even have healthy looking turf for the most part, but then all of a sudden patches of brown pop up and leave you with nothing but questions. The most likely questions are ”what is this and how did it get into my lawn?”

The interesting thing is you had fungus in your lawn the entire time, even when your lawn was looking green and disease free. Our lawns all contain fungus, in fact, fungi are pretty much everywhere in our lives! But most of the time our lawns, just like our bodies, keep fungi under control before they have noticeable affects. Think of your lawn as having an immune system just like your body does.  The real question you should be asking is why did your lawns immune system fail you and let in this disease?

Here’s the deal… in order for a fungal disease to really take hold, it needs 3 things. A host, which in this case is your lawn, a pathogen which in this case is the fungus spores (and they are everywhere), and ideal environmental factors (humidity, heat, cool, moisture, etc).

We already established that your lawn is the host, and the pathogens, which are the fungus spores, are always in your lawn. Those 2 are the constants. But the third requirement, environment, is the variable. When a fungus can really take hold it’s because there are stressors in your lawns environment.

These stressors include but are not limited to: 

-Heat and drought

-Excessive Moisture

-Nutrient Imbalances and Deficiencies

-Excessive Application of Herbicides

-Humidity

-Increased Foot Traffic

-Cutting Lawn too Short

Anything that can cause stress to your lawn can weaken your lawns “immune system” and allow fungus and disease to take control. 

Prevention and Treatment

This strategy uses 2 fungicides.  Without getting too technical, fungicides fall into ‘groups’ and different groups prevent or treat different types of fungi. In this strategy group 3 and group 11 will be applied which covers most of the fungi that could cause problems to your lawn. 

When to Apply Fungicides

Fungicides are most useful when applied right before times of stress. For cool season lawns this is without a doubt right before the heat of summer. Whenever we get those first really hot days, our cool season lawn instantly gets weakened. Again, think of your immune system. You are more likely to get sick if you are hot and dehydrated since your immune system is weakened.

Applying preventative fungicides right before these harsh conditions is a lot like feeding your body essential vitamins and nutrients right before an outbreak of seasonal cold or flu. 

For warm season lawns there’s really 2 times where your lawn is most stressed. The first time is heading into summer when rain and humidity ramp up. The second time is when soil temps start to decrease after the peak of summer, heading into fall. Apply preventative fungicide leading up to these 2 transitional times. 

About the Fungicides in This Strategy

Scotts DiseaseEx

Scotts DiseaseEx (active ingredient Azoxystrobin) is a group 11, granular fungicide that gets broadcasted over your lawn using a broadcast spreader. It helps control Brown Patch, Stem & Stripe Rust, Red Thread, Powdery Mildew, Pythium, Southern & Typhula Blight, Pink Patch, Nercrotic Ring Spot, Summer Patch, Yellow Patch and more.

Scott’s Disease Ex can be used as a preventative and a curative treatment (curative means the disease is already present). A 10lb bag can cover up to 5,000 s/f which gives us an application rate of 2lbs per 1000 s/f, but you can apply at higher rates for a curative treatment (3-4lbs per 1000s/f).

This product can be applied every 14-28 days, depending on how heavy you apply each time. Do not exceed 37 lbs per 1000 s/f in a single season. After applying, this product should be watered in. 

Propiconazole

 

Propiconazole is a group 3 fungicide that is great as both a curative treatment and a preventative but in this strategy it will mostly be used as a curative treatment. Propiconazole prevents and controls Rusts, Pink & Gray Snowmolds, Gray Leaf Spot, Zoysia Patch, Dollar Spot, Summer Patch, Anthracnose, Leaf Spot, Brown Patch, Powdery Mildew plus more.

This product is a concentrate and get’s diluted in water and spread over your lawn with a tank sprayer. You have a couple of different options when it comes to tank sprayers, depending on your needs:

If you have a very small lawn and/or are just planning on using it for spot treatments you can get a way with a small 2 gallon hand pump sprayer here: Chapin 2 Gallon Sprayer

If you have a large lawn and plan on doing a a decent amount of spraying throughout the year, whether it’s fungicides, herbicides, or for other uses, consider a 4 gallon back pack sprayer. You can use this less expensive manual pump sprayer: Field King Sprayer 4 Gallon

Or you can use a battery powered 4 gallon back pack sprayer (like I use): Chapin 4 Gallon Sprayer Battery Powered

In my opinion investing in a good sprayer is important. I use it for a lot of lawn applications such as post emergent weed control and also insect control around my home and garden areas. You can also use back sprayers for organic treatments such as bio stimulants, neem oil foliage sprays for plants, and many other uses around your landscape!

For use as a curative, mix 2 oz per gallon and target just the areas that are diseased. 

This product does not get watered in so let it sit after applying. 

Simple Treatment and Prevention Strategy

For Cool Season Lawns

Here’s the deal… for cool season lawns you should mostly be concerned about fungus in late spring/early summer. That’s when your lawn is most vulnerable and fungus can overtake your lawn and kill infected areas.

For prevention, apply Scott’s DiseaseEx in late spring/early summer before the real heat kicks in.  Apply at 2-3 lbs per 1000 s/f.  to your entire lawn.

If you’re already starting to see disease pop up then apply with the curative rate of 3-4lbs per 1000 s/f rate, and apply whenever you notice that your lawn is infected, even if it’s early spring. Diseases such as Red Thread and Leaf Spot can hit cool season lawns before the summer hits so always be on the lookout since early intervention is so key in combatting disease. 

 Also, for a curative treatment have the Propiconazole in a tank sprayer on hand just in case you see signs of disease. Some diseases are widespread, while others may appear as specific patches. If you notice specific problem areas, or patches, then spot treat those areas with Propiconazole mixed at the curative rate of 2 oz per 1 gallon of water. If you see a widespread fungus such as leaf spot throughout your lawn, then spray your entire lawn with the Propiconazole. Just note that you should wait a couple days after applying Scott’s DiseaseEx before spraying Propiconazole. If disease problems continue I would do a follow up treatment with the Propiconazole about 20 days later. 

Now, if you have an ugly history of fungus problems and want to use a more aggressive approach you can apply the Scott’s DiseaseEx once a month. Don’t forget, the maximum yearly allowance is 37lbs per 1000 s/f. So applying at 2lbs per 1000 s/f monthly means you don’t have to worry about overapplying.

You can start applying in the middle of spring and every four weeks re-apply. Once fall hits you can back off.  Of course, you could also choose a less extreme plan and apply just couple of times from spring to late summer. You really have to gauge how aggressive you want to be.

By the end of the summer, most cool season lawn fungus problems should fade as your lawn begins to strengthen again as soil temps decrease. 

For Warm Season Lawns

For warm Season Lawns  I’m going to recommend a more prolonged preventative approach since there is a longer period of time where warm season lawns are vulnerable to fungus attack. Unlike cool season lawns which face their biggest transition heading into the heat of summer, warm season lawns have 2 distinct transition periods: Heading into the wet and humid summer, and then again when temperatures cool during the fall.

If you have a history of fungus problems in your warm season lawn I would suggest applying the Scott’s DiseaseEx at a rate of 2-3 lbs/per 1000 s/f at least 2 times during the season (late spring and late summer).

The Propiconazole should be on hand and ready to be mixed in a tank sprayer to treat any disease that does pop up. The Propiconazole should be mixed at the curative rate of 2 oz per gallon. 

Now just like with cool season lawns, you can build or take away from this strategy. But for the most part if you’re concerned because you think you’ve had some fungus problems in the past, applying the DiseaseEx twice should be a big help.

If you have a history of bad fungus and disease problems or are actively trying to fight off disease then I would increase the Scott’s DiseaseEx applications to 3 or 4 times per year for longer coverage. 

Of course, if you don’t have a history of fungus and disease you may choose to apply only once, most likely either late spring or late summer. You may even choose not to apply Scott’s DiseaseEx at all. Instead you could just have Propiconazole on hand just in case you see some disease flare up.

Overall, you have to determine how aggressive you want to be based on your lawns history. Just know that Scott’s DiseaseEx and Propiconazole work as a great team. I like to lean on the Scott’s DiseaseEx more for a preventative strategy and the Propiconazole for more of a curative strategy. 

Can You Apply Fungicide and Fertilizer at the Same Time?

Yes, for the most part fertilizer and fungicides can be applied at the same time. Just make sure that for fungicides such as Propiconazole that benefit from staying on the foliage you should wait on irrigating for at least 24 hours. 

Cultural Ways to Prevent Lawn Fungus

Following the correct cultural practices are a great way to reduce problems associated with fungus and disease and also will make you less likely to have to rely on fungicides:

• Feed your lawn regularly and keep the nutrients balanced (NPK)
• Mow taller, more often, and with sharp blades
• Follow the important summer lawn care tips found here: Summer Lawn Care
• Bag your clippings! I know this causes a lot of controversy among landscape professionals but personally I’m a big advocate of collecting your clippings. See my rant about this here: Leave Clippings on Lawn or Not?
• Avoid watering at night. Night watering keeps your lawn too wet for too long and fungi can thrive under these conditions. 
• Use slow release fertilizers low in nitrogen and high in potassium during seasonal transitions. Synthetic fertilizers that are high in nitrogen will encourage quick blade growth. This is fine for when conditions are ideal, but during seasonal transitions when the lawn is stressed you want to minimize blade growth and allow the grass to focus on overall health and combatting disease. Using a product such as Stress Blend 7-0-20 is a great fertilizer to apply leading up to period of stress for your lawn. The increase in potassium is what helps aid in the overall health of your grass.

Other Advice

I want to point out that a lot of fungus and disease problems can look a lot scarier then they are. A lot of problems can be solved by sticking to the cultural prevention tips above. If you follow these cultural practices, most of the time your lawn will be able to grow its way out of the disease since a lot of these problems occur on the leaf blades themselves. When your lawns ‘environment’ improves it will put on new growth and you’ll be cutting off damaged blades when you mow, making way for new, healthier foliage.

Common Types of Lawn Fungus

Curious about what type of fungus you might have? While the strategies outlined above apply to most lawn fungus and disease problems feel free to learn more about some of the more common diseases and how to identify below. You can also take a look at the Disease Identification Chart to Id the problem you have in your lawn.

Dollar Spot– Appears as small, round patches of light tan grass about the size of a silver dollar.

Brown Patch– Mostly circular patches that start out as yellow and can turn into brown, dead grass. Patches can be several inches to several feet in diameter. 

Powdery Mildew– Appears as white powder along leaf blades. Usually doesn’t cause a lot of destruction in grass. 

Leaf Spot– Leaf blades will have spots that are brown/purple. 

Red Thread– Easy to identify by its reddish pink threads that appear at the top of leaf blades. Usually doesn’t cause a lot of destruction and can be fixed with improving cultural practices. 

Summer Patch– Irregular circular patches of dead grass. Grass blades die back from the tip. 

Rusts– Blades will be coated with orange-red spores that give it a rust color. 

Check Out These Posts Next

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Core Aeration and Overseeding

How to Fertilize Your Lawn

Lawn Dethatching: Everything You Need to Know

How to Kill Crabgrass

White Grubs: Prevention and Treatment

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