How to Get Rid of Powdery Mildew on Your Lawn

powdery mildew on the top of a green leaf

What’s that white powder on the lawn? Either your turf is suffering from powdery mildew, or the little red hen spilled her flour on your yard. If it’s the former, you needn’t panic –– powdery mildew is not a severe turfgrass disease, as long as you treat it right away. 

How do you control powdery mildew? Why is it growing on your lawn? Our guide to the turfgrass disease has got you covered.  

What is powdery mildew?

Powdery mildew is the name for multiple plant diseases with similar symptoms caused by closely related fungi. Most powdery mildews are recognized for the white, powdery spots that develop on infected plant stems, fruits, and leaf surfaces. 

Powdery mildew can affect many healthy plants in the landscape, including flowers, trees, woody ornamentals, turf, weeds, vegetables, and fruits. In the context of this article, we’ll be covering how powdery mildew affects your turfgrass. 

White powder taking over your landscape isn’t a pleasant thought, but don’t be alarmed. Powdery mildews are host-specific, meaning powdery mildew fungi don’t generally spread to different types of plants. For example, the fungus that causes powdery mildew in your grass isn’t going to infect your begonias and ​​cucumbers (although it can affect your cereal grains, such as wheat and oats). 

Will powdery mildew kill my turf?

Powdery mildew is not a serious turfgrass disease and generally does not kill turf. However, if you ignore powdery mildew for too long, the weakening turf may eventually succumb to other stressors, resulting in dead grass

How to identify powdery mildew on turfgrass

If your grass looks like it has been sprinkled with flour or talcum powder, that’s a tell-tale sign of powdery mildew. Here are the common symptoms to look out for: 

  • White, isolated spore masses develop on the infected leaf
  • The white masses begin to enlarge and cover the whole grass blade
  • Tiny, black fruiting bodies develop within the powdery masses
  • Severely infected grass is turning yellow or dying

What causes powdery mildew in the lawn?

The pathogen that causes powdery mildew in grasses is Blumeria graminis (formerly Erysiphe graminis). 

If you have a Kentucky bluegrass lawn, then your turf is highly susceptible to powdery mildew. Powdery mildew will occasionally infect fescue grasses, but fescue is more resistant to the disease than Kentucky bluegrass. 

But powdery mildew needs more than just a susceptible plant. It requires the right environmental conditions, too. Here’s what the fungus needs if it’s going to infect your lawn: 

  • Shade
  • Poor air circulation
  • High humidity (leaf wetness is not necessary, but high humidity is) 
  • Air temperatures between 60 and 70 degrees Fahrenheit
  • Excessive nitrogen fertilizer

How to get rid of powdery mildew in the lawn

You can’t change your humid climate, but you can change your lawn’s cultural environment. Compared to controlling other turfgrass diseases, powdery mildew treatment is relatively simple. It only requires a few changes to your lawn care routine. All you need to do is: 

  • Decrease shade in affected areas by trimming or pruning plants that are blocking sunlight. 
  • Remove, transplant, or trim plants that are inhibiting air circulation around the infected turf. 
  • Adjust your irrigation routine to prevent shady areas from staying wet for too long. The best time of day to water is in the morning before 10 a.m. Avoid watering in the evenings. Water the lawn infrequently and for long periods. 
  • Avoid heavy nitrogen applications.
  • If you cannot modify the turf’s environment, the Clemson Cooperative Extension recommends applying fungicides containing myclobutanil, propiconazole, or triadimefon. Always use fungicides according to the product label. 

How to prevent powdery mildew in the lawn

Once you remove powdery mildew from the yard, follow these preventative measures to keep the disease out for good:

  • Reseed shady areas with a mildew-resistant Kentucky bluegrass cultivar and shade-resistant fine-leaved fescue. 
  • Discourage shade in the yard by pruning and trimming landscape plants. 
  • Ensure good air circulation by pruning and trimming landscape plants. 
  • Maintain proper watering techniques.
  • Test your soil and develop a fertilization regime that’s suitable for your lawn.
  • When planting new plants, ensure the spacing does not inhibit airflow or sunlight.

How does powdery mildew spread in the lawn?

Powdery mildew fungi are obligate parasites, which means their survival depends on a living host. Unlike many other turfgrass diseases, which overwinter in dead plant debris or thatch, powdery mildew overwinters in living grass tissue. The disease produces spores in spring that the wind spreads to healthy grasses. 

FAQ about turfgrass disease

1. What other turf diseases can infect my lawn?

Powdery mildew might not be a severe threat to your lawn, but several turfgrass diseases can destroy your yard if you’re not vigilant. Turfgrass diseases that can infect your yard include: 

Anthracnose
Brown patch
Dollar spot
Fairy ring
Gray snow mold 
Leaf spot and melting out
Pink snow mold 
Red thread
Rust 
Summer patch

2. How do I prevent grass diseases on my lawn?

The secret to keeping a yard disease-free is proper lawn maintenance. Fungal diseases thrive in lawns with poor maintenance conditions, such as excess thatch, wet grass, and weak root systems. The healthier your turf, the more resistant it will be against turfgrass disease. 

So, what lawn care chores should you be adding to your honey-do list? Here are 15 lawn care treatments that will help your lawn combat disease: 

Remove leaves and other debris from the yard. Many fungi remain dormant in plant debris. A thick layer of leaves also weakens the turf by blocking sunlight.
Mow the grass regularly (and correctly). Always mow your lawn at your grass type’s recommended mowing height. Your lawn may be susceptible to disease if the grass is too tall or too short. And remember, never cut off more than ⅓ of the grass blade during a single mow. 
Leave behind grass clippings. Grass clippings are a healthy, organic mulch for your lawn that decomposes quickly. Do not leave behind diseased grass clippings; otherwise, the disease may spread.  
Perform proper irrigation practices. Prolonged leaf wetness is a common cause of turfgrass disease. The best way to minimize wet grass is to water at the right time of day. Water early in the morning before 10 a.m., and avoid watering in the evenings. Water your lawn infrequently and for long periods to promote a healthy root system. 
Invest in a sprinkler system. Watering the yard can be time-consuming. Why not let an automatic sprinkler do the work for you? After all, a sprinkler system can measure just the right amount of water your lawn needs and spread it uniformly.
Plant grass seed that’s disease-resistant and suitable for your lawn.  Talk to a local lawn care professional about whether warm- or cool-season grass is best for your yard. You also may want to consider growing a disease-resistant cultivar. 
Test your soil. A healthy lawn needs healthy soil. Perform a soil test to determine what nutrients your soil is lacking. 
Fertilize your grass. After a soil test reveals the lawn’s nutrient levels, create a fertilization routine that will meet your lawn’s needs.   
Aerate compact soil. Compact soil prevents water, nutrients, and oxygen from accessing your lawn’s root system. Core aeration relieves compact soil by creating small holes in the ground. 
Remove thatch that exceeds ½-inch thick. Thatch is the dead organic matter that accumulates between the turf and soil surface. A thin thatch layer acts as a healthy mulch for the lawn, but a thick layer may harbor dormant fungus. 
Overseed the lawn. Encouraging new growth with routine overseeding helps your yard remain dense and green.
Remove existing weeds. Your lawn needs to devote its energy to growing healthy and strong –– not competing against weeds. If your yard has a severe weed problem, the turf will need to compete for moisture, nutrients, water, and sunlight. 
Apply pre-emergent herbicide. You can prevent weeds from popping up in the lawn by applying a pre-emergent herbicide. 
Control grubs and other pests. Grubs will feast on your lawn’s root system, resulting in a weak and stressed lawn. 
Spread compost across the lawn. Turn your compost into a nutritional organic fertilizer for your lawn. Rake a compost top dressing across the yard or apply compost tea with a sprayer.

3. What if I can’t identify the fungus on my lawn?

Correct identification of the fungus infecting your lawn is essential if you want to achieve effective control. The control methods that may get rid of one disease are not guaranteed to remove other lawn diseases. If you misidentify the fungus, you risk improper treatment and the disease worsening. 

When identifying the fungus proves difficult, turn to a local diagnostic lab or turfgrass pathology lab for help. These labs specialize in the accurate diagnosis of infected turf and are typically located at state universities.

Call in the pros for help

When your lawn is in the grips of a turf disease, it’s essential to act fast. But sometimes, finding the time to battle fungus is nearly impossible. If you’re concerned that you can’t tackle the disease in time, hire a local lawn care professional to handle the job. 

Not only can a professional mend your lawn, but they can also help prevent future outbreaks and give you back your free time. Instead of spending your weekend controlling a fungus, you spend it doing what you enjoy (or help the little red hen bake her bread)?

Main Photo Credit: Dmitry Brant | Wikimedia Commons | CC BY-SA 4.0

Jane Purnell

Jane Purnell is a freelance writer and actor in New York City. She earned her B.A. from the University of Virginia and enjoys a warm cup of French press coffee.