How to Treat Lawn Fungus

lawn with dead or yellow spots

The best way to treat lawn fungus is by combining proper lawn care practices with good quality fungicides suitable for the fungi damaging your turf. Most homeowners prefer to leave fungal treatments to the pros since faulty applications can drastically reduce effectiveness, but a DIY approach is also in the cards if you know what you’re doing.

Keep reading to learn what causes lawn fungus, how to apply a fungicide correctly, and the top lawn care practices that help treat and prevent lawn diseases.

What causes lawn fungus

Lawn fungus is caused by parasites that infect grass plants, slowing their growth and damaging tissue and essential functions. Colonized turf loses its healthy green color, starts to wilt, wither, and, in some cases, dies.

While the ideal temperature pathogenic fungi need to thrive varies, most need high humidity to grow and multiply. Rainy summers, foggy springs, autumns with heavy dew, and winters with thick snow blankets often precede a fungal disease.

Stressed turf is more vulnerable to infestation, and your lawn is more at risk of being attacked by fungi if exposed to:

  • Drought
  • Extreme temperatures
  • Over or under-fertilization
  • Overwatering
  • Scalping
  • Compacted soil
  • Thatch 

Signs of lawn fungus

Rust lawn disease
NC State Cooperative Extension

When lawn fungus moves in, your lawn shows signs of distress such as:

  • Irregular or circular patches with straw-like or brown grass. More unusual colors, such as orange (leaf rust) or pink (red thread, pink snow mold), can also appear.
  • Rings of off-color grass with healthy turf in the middle–the “frog-eye” appearance.
  • Bare patches with wilted, dead grass.
  • Straw-like, tan, or brown spots (sometimes pink, yellow, or other colors) on leaves.
  • Blighted leaves with no individual lesions.
  • Brown or black rot spots at the sheath, crown, and root level.
  • Dark or whitish mycelium on the soil and plants.
  • White, gray, or orange powder covering the blades of grass.

A faulty lawn care routine or stressful environmental conditions can also cause some of these symptoms. In fact, more than one fungal disease can be confused with signs of drought.

Before starting a fungal treatment, especially chemical, ensure you’ve got a fungal infection and not a faulty sprinkler system or a bad mowing technique.

The surest way to diagnose a fungal infestation is by taking a grass sample to a nearby plant pathology laboratory for testing. You’ll also discover the fungus you’re dealing with and the best treatment.

How to control lawn fungus

wet grass in a lawn
VSargues | Canva Pro | License

With an active fungal disease, your main focus is to stop the spread of fungi across the healthy grass. Follow a few simple steps:

  • Clean your lawn care tools and equipment after each use.
  • Perform lawn maintenance tasks on the infected area last.
  • Remove grass clippings from your lawn.
  • Reduce foot traffic across your lawn.
  • Avoid mowing your grass while it is wet.
  • Water your lawn in the early morning between 6 a.m. to 10 a.m.
  • Water deeply, aiming for three 20-minute sessions weekly.
  • Remove heavy morning dew from the grass canopy.
  • Don’t irrigate when it rains.
  • Aerate and dethatch annually to improve drainage.
  • Trim trees and shrubs to increase air circulation and sun exposure.

Adjust the pH

You can also tweak the fertility and pH of the soil to weaken the fungi and strengthen your grass. However, these measures depend on what fungus is infecting your lawn. For example, dollar spot and red thread disease can be pushed back by applying small amounts of nitrogen. Brown patch, on the other hand, loves nitrogen.

Start by identifying the fungus messing with your turf. Each lawn fungus leaves specific signs you can use to recognize it.

Lawn diseaseSigns and symptoms of fungal disease
Dollar spotGold, dollar-sized, circular spots of yellow, straw-colored. Or light brown grass
Red threadReddish or pinkish irregular patches up to two feet wide
Brown patchIrregular brown patches up to a few feet wide; often with green, sunken centers
Large patchSmall, irregular areas of tan-orange grass up to 12 inches wide
Yellow patchCircular, yellow to light-brown patches five inches to a few feet wide
Pythium blightSmall circles of withering, blackened, or reddish-brown grass 2 to 6 inches wide
Fairy ringCircular or semi-circular bands of taller, greener grass or dry, straw-colored to light brown turf; often with mushrooms
Gray leaf spotIrregular blighted patches; bleached, twisted leaves with small, water-soaked lesions; sometimes covered in grayish spores
Fusarium blightGrayish-green areas with a circular shape a few inches to a few feet wide
Powdery mildewLight green to whitish areas; grass appears powdery
Spring dead spotCircular spots of bleached-out, dead grass six to 12 inches wide; often merge into larger patches
Summer patchYellow to tan circular patches with wilted and dead grass up to one foot wide
RustGolden yellow to orange-rust irregular patches; grass appears covered in rust-orange powder
Leaf spotIrregular patches with off-color turf; grass stems, sheaths and blades have elongated or circular light brown spots
Melting outPatches of yellow to blackish-brown wilted or dead grass; dark brown rot on roots and crowns
Take-all Root RotIt starts with chlorotic, yellow to light green patches; grass eventually turns brown, thins out, and dies
Leaf blightIrregular patches with blighted, straw-colored, or brown grass; often appear overnight
Gray snow moldWhitish or straw-like circular or irregular patches; gray mycelium is often visible; found near receding snow banks
Pink snow moldPink, white, or tan circular patches up to one foot wide; often appear when the snow melts in the spring
AnthracnosePatches of various sizes with bright yellow, reddish, or bronze grass; basal roots have rot lesions

If you are still in doubt send a grass sample to a plant pathology lab for testing. Contact the closest Cooperative Extension Office for advice, or connect with a lawn care professional.

How to treat lawn disease with fungicide

Spraying fungicides on lawn with a one-hand pressure sprayer
welcomia | Canva Pro | License

Typically, you can deter small fungal infections by correcting lawn maintenance habits and protecting your turf from environmental stress.

But that’s not always the case. Sometimes, you get a resilient type of fungi that is hard to stop and keeps returning year after year despite diligent lawn care efforts–enter fungicide.

Types of fungicides

Fungal killers are divided into two categories that fight the disease in different ways:

  • Contact fungicides
  • Systemic fungicides

Contact fungicides: A preventive shield

Contact fungicides form a protective layer that coats the blades of grass, preventing fungi spores from penetrating the plant tissue. They are called non-penetrant fungicides because the solution never enters the plant but only acts on its surface, destroying the spores and hyphae.

Best results: Contact antifungals are effective for disease control only when used as a preventive measure on healthy plants. They can’t help grass plants already colonized by spores. You’ll get the best results by applying this fungi killer before the first signs of infection.

Frequency of application: Contact fungi killers are easily broken down by rain, heavy dew, lawn irrigation, mowing, and foot traffic. Even without these factors interfering, you need to reapply the fungicide every seven to 14 days to extend protection to new growth.

Systemic fungicides: Powerful but not invincible

Also known as penetrant fungicides, systemic formulas enter the plant, kill the spores and hyphae, and protect from future infection. Some travel locally while others move from roots to leaves.

Best results: Systemic fungicides have their limits. They can deal with a few spores and hyphae structures starting to invade a plant but can’t cure extensively colonized and damaged grass. The curative part works best when systemic fungicides are applied within 24 to 72 hours of infection.

Frequency of application: Since they work inside the plant, systemic fungi killers are less sensitive to exterior factors like rain and dew and last seven to 28 days. Some can also travel into new leaves and extend their protection to new growth.

Natural fungicides

Some lawn owners prefer to try a natural product for fungus control before turning to chemical products. Some of the most common natural antifungal ingredients you can try in a DIY fungicide are:

  • Neem oil: Neem oil prevents anthracnose, leaf spot, rust, powdery mildew, gray mold, and leaf and blossom blight disease. Mix 1 ounce of neem oil with one gallon of water.
  • Clove oil: It’s a contact fungicide you can use to prevent brown patch. Mix two tablespoons to one gallon of water.
  • Potassium bicarbonate: A better alternative to baking soda (the sodium can damage plants), potassium bicarbonate fights powdery mildew. Mix one tablespoon of potassium bicarbonate, ½ teaspoon of liquid soap, and one gallon of water.

Pro tip: 2.5 gallons of natural fungicide solution covers 1,000 square feet.

Broad-spectrum vs. narrow-spectrum fungicides

Broad-spectrum fungicides fight multiple diseases caused by various fungi groups. However, the downside is that beneficial fungi in the soil are also damaged.

Narrow-spectrum fungicides are only effective against a few related diseases. They’re more like a surgical intervention. You kill the nasty guys, but the good fungi go on with their lives. The downside is that you need to be 100 percent sure what disease you are dealing with.

Fungicide resistance

Just like bacteria and antibiotics, fungi develop resistance if you use the same treatment every time. Experts recommend rotating treatments with different active ingredients and alternating contact and systemic fungicides.

How to apply fungicides

Most homeowners prefer to leave the fungal treatments to the professionals. They get better results and have access to more powerful fungicides.

For systemic and contact fungicides, timing is essential but not the only factor that drives success. Follow four simple steps to get the most out of your fungal treatment:

Step 1: Application timing is important

Typically (but not always), fungi attack turfgrass when it is entering or exiting its dormancy period. For warm-season grasses, these periods fall during the spring and fall. For cool-season grasses, this period is the summer.

Sometimes, symptoms appear months after the fungal attack. For example, spring dead spot attacks Bermudagrass in the fall and early winter, but you won’t see the signs until the next spring when your grass greens up. The best time to intervene is the early fall.

Weather is also an excellent clue. Remember, high moisture activates fungi that stay dormant in your turf.

Step 2: Wear safety gear.

Fungicides are dangerous chemicals. Keep pets and kids away from the treated area until the solution dries. Additionally, always wear protective gear, including:

  • Safety glasses or goggles
  • Closed-toe footwear
  • Long sleeves
  • Gloves
  • A mask

Step 3: Follow the manufacturer’s instructions

Pay attention to the application rate and any technical details. Most brands include detailed tables with specific indications for each fungal disease you can treat.

Generally, experts recommend:

  • Spread two pounds of solution per 1,000 square feet for preventive applications and three to four pounds per 1,000 square feet for curative applications.
  • Use 60 to 60 pounds of water pressure per square inch.
  • Opt for a hollow cone nozzle that sprinkles medium-fine particles.

Step 4: Repeat the application

Apply the fungicide as many times as indicated on the label or until the exposure period has passed. Severe infestations require more application with less time in between.

How to prevent fungal infections

Fungi become active during periods with excessive moisture, including overwatering your lawn. The pathogens also thrive in stressed, weakened turfgrass. Here are some effective lawn care practices for a resilient lawn to help prevent fungal infections:

  • Overseed annually with a disease-resistant cultivar: Fill in bare spots and keep your turfgrass healthy by overseeding with a disease-resistant variety annually.
  • Practice optimal mowing: Keep your lawn mower blades sharp. Don’t mow wet grass. Never cut more than ⅓ of the grass blade length. Keep your grass at the right height for its type.
  • Fertilize with nitrogen: Use slow-release formulas. Use one pound per 1,000 square feet and follow the recommended annual amount for your type of grass.
  • Opt for natural alternatives: Leave grass clippings on your lawn, and apply a layer of compost yearly to improve soil structure and add nutrients.
  • Test your soil annually: Check nutrient and pH levels and use the data to amend your soil.
  • Water wisely: Do a sprinkler audit each year and repair or replace broken sprinkler heads. Water deeply, aiming for three 20-minute sessions weekly.
  • Improve drainage: Core aerate your lawn annually to reduce soil compaction and improve drainage.
  • Remove thatch: Thatch is a layer of plant roots, stems, and leaves between your turfgrass and the soil. Fungi use it to hide and feed, especially during dormancy periods. Remove your thatch layer annually when it is ½-inch thick or more.
  • Manage weeds: Competing plants steal nutrients, water, and sunlight from your grass. Follow a weed control schedule to ensure your turf grows healthy and strong.
  • Control pests: Nasty lawn pests like chinch bugs and grubs damage your grass and expose it to more severe fungal infections. Keep an eye out for signs of pest infestation and act quickly to deter the nasty buggers.

FAQ about how to treat lawn fungus

What is the best treatment for lawn fungus?

The best treatment for lawn fungus combines correct lawn care with a mix of contact and systemic fungicides rotated periodically to prevent resistance development.

What is the best natural fungicide for lawns?

Neem oil is an excellent choice for natural fungus control. It’s an effective contact fungicide that deters nasty insects and feeds the grass and soil with nutrients. Other options also include potassium bicarbonate, ammonium bicarbonate, citric acid, and clove oil.

What are the most common causes of lawn fungus?

The most common cause of lawn fungus is excessive moisture combined with a stressed, weak turfgrass.

Call a pro for effective lawn fungus treatment

Are you tired of spending money on fungicides with less-than-stellar results? Go for a pro approach this year. Let Lawn Love connect you with top-notch lawn care companies who can treat lawn fungus effectively. Take advantage of their experience and professional products and get your lawn back to health.

Note: Lawn Love may get a referral fee for matching you with contractors in your area.

Main Photo Credit: MaYcaL | Canva Pro | License

Sinziana Spiridon

Sinziana Spiridon is an outdoorsy blog writer with a green thumb and a passion for organic gardening. When not writing about weeds, pests, soil, and growing plants, she's tending to her veggie garden and the lovely turf strip in her front yard.