Use these products and maintenance practices to prevent and treat lawn fungus. Combining these strategies with a simple lawn care program is the best way to prevent disease from taking over your lawn.
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 most likely had fungus in your lawn the entire time, even when your lawn was looking green and disease free. Our lawns all contain fungus, but there’s usually no visual effects, unless certain conditions are met.
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, moisture, poor drainage, etc).
We already established that your lawn is the host, and the pathogens, which are the fungus spores, are already 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
-Poor Drainage
-Increased Foot Traffic
-Cutting Lawn too Short
Anything that can cause stress to your lawn can allow fungus and disease to take control.
When to Apply Fungicides
Overall, I try not to apply fungicides to my lawn. It’s not something that’s a regular part of my lawn care program, I only do it when I anticipate that fungus will be a problem. Fungicides are expensive, and I always try to minimize chemical inputs in my lawn. But, if I see conditions forming that will likely cause an outbreak of fungus and disease that could destroy large portions of my lawn, I will take early action with fungicides. Here’s some of the things to consider when trying to determine If and when you should apply fungicides:
1. Consider When Past Fungus Problems Occurred
If you had bad fungus and disease problems in years past, especially in the previous year, think about when those problems started. Was it in the wet spring weather, or more in the heat of the summer? Be ready to apply fungicide as a preventative leading up to those times that are historically bad fungus times in your lawn.
2. Period of Excessive Humidity and Moisture
A lot of fungus problems occur when there’s high humidity. Your lawn, and most plants, do not like humidity. Monitor the weather and be on the lookout for high humidity or a rainy stretch of weather. Get your fungicide down as a preventative before these periods of excess moisture.
3. Seasonal Shifts and Periods of Stress
In general, seasonal shifts are times of stress in your lawn. Transitioning from winter weather to spring weather, or spring to summer can be create stressors in the lawn that can make it easier for fungus to take hold. Try to apply preventative fungicides before these big seasonal shifts.
Prevention and Treatment Products
When it comes to lawn fungus and disease, prevention and early intervention is so much more effective then treating an already infected lawn.
Without getting too technical, fungicides fall into ‘groups’ and different groups use different modes of action to prevent or treat fungus. Using a combination of different groups helps to give us different angles of attack when trying to combat the fungus. That’s why you’ll notice with my product recommendations below we are using products that combine Group 11 and Group 3 Fungicides.
1. Propicanozole and Azoxystrobin
Propicanozole and Azoxystrobin are two separate liquid fungicides that can be used separately, but I recommend mixing them together. This will give you two separate modes of action and overall will give you better prevention and control over a wider range of fungus problems.
You’ll notice both these products are expensive, but they are concentrates, meaning they get mixed with water in a tank sprayer. This means you get a lot of mileage out of just a small amount.
For smaller lawns you can use a Chapin 2 Gallon Sprayer sprayer, for larger lawns consider using a Chapin 4 Gallon Sprayer Battery Powered.
Follow the labels for application rates and instructions. The preventative rates are for prevention, meaning you don’t see any signs of fungus yet. The curative rate is for when you already see fungus in your lawn.
2. Headway G
Headway G is a combination of Propicanazole and Azoyxstrobin, just like the products mentioned above, only instead of a liquid it’s in granular form. This means it gets put into a spreader and broadcasted over your lawn instead of sprayed. If you’re intimidated by spraying your lawn or would just rather use a granular product then this is a great choice.
3. Pillar G
Pillar G is another great granular product that once again, combines a Group 3 and Group 11 Fungicide. Instead this time the active ingredients are Pyraclostrobin and Triticonazole. Pillar G is really for a preventative more then a curative so apply this product before your lawn is showing signs of fungus. This is actually my favorite product to put down as my first preventative in spring. After that I switch to a combo of Propiconazole and Azoxystrobin. With fungicides, it’s good to mix things up since using the same product over and over can cause fungicide resistance, and won’t be as effective.
4. Clearys 3336 for Gray Leaf Spot
If you’ve identified Gray Leaf Spot to be your main problem then go with Clearys 3336. This is a better product for Gray Leaf Spot than Propicanazole. I still recommend mixing this with Azoxystrobin like we have in the strategies above, but for gray leaf spot sub out the Propicanzole for Clearys 3336. Once again, follow the label for application rates and coverage.
Non Chemical 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, especially if you see signs of fungus.
- 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 non chemical 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.
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Charles Reynolds says
Hello Mark, Thanks for all the good advice! I had written before asking about how to control moss problems? Seems to be more predominant on the shade side of the house. I assume the moss is not considered a fungicide? With that said is liming a good way to help curb the problem? I understand that iron is also helpful to control spreading moss which seems to act like a cancer wiping out all grass in its path! Thanks for you help. Charles Reynolds, Precast Outdoor Fireplaces
George says
Hi Mark,
I just noticed what I believe is rust in my lawn. It was on my mower and my shoes last time I mowed and walked my lawn. I read your article on fungus and I read a separate article on lawn rust. It recommends a high dose of nitrogen but I see you recommend the disease x. I’m looking for a cost effective product since I have about 70,000 sq ft to do. I do have a broadcast spreader and a tow behind sprayer. Any recommendations would be greatly appreciated! Thanks much!
-George
Francis Murtagh says
Thanks Mark
I’m plagued with white circular patches which are about 6 inches in diameter.
This is a 6 month old renovated lawn and it was looking great but now it looks terrible.
Will Proplant work to kill the fungus ?
What type of fungus is it do you think?
I live in Ireland..
[email protected]
Charles Reynolds says
Hello Mark, Appreciate all your efforts! I had written before asking for help on moss control? Did I overlook your reply? Really not sure what causes moss and what the cure is? Thank you! Charles Reynols