What’s that white powder on your 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, don’t panic–powdery mildew is not a severe turfgrass disease as long as you treat it immediately.
How do you get rid of powdery mildew? Why is it growing on your lawn? Our guide to this turfgrass disease has got you covered.
What is powdery mildew?
Powdery mildew classifies multiple plant diseases with similar symptoms caused by related fungi. The pathogen that causes powdery mildew in grasses is Blumeria graminis (formerly Erysiphe graminis). Most powdery mildews produce white, powdery spots that develop on infected plant stems, fruits, and leaf surfaces.
Powdery mildew can affect many healthy landscape plants, including flowers, trees, woody ornamentals, turfgrass, weeds, vegetables, and fruits. Mildew taking over your landscape isn’t a pleasant thought, but don’t be alarmed. Powdery mildews are host-specific, meaning they don’t spread to different types of plants.
For example, the fungus that causes powdery mildew in your grass isn’t going to infect your begonias, cucumbers, or zucchini.
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 on infected leaf blades
- 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 on your lawn
Some grasses are more susceptible to powdery mildew than others. Powdery mildew is one of the most common Kentucky bluegrass diseases, but it’s also common on annual bluegrass, Bermudagrass, bentgrass, Zoysiagrass, and tall fescue.
Powdery mildew needs more than just a susceptible plant. It requires the proper environmental conditions, too. Here’s what the fungus needs to thrive on your lawn:
- Shade
- Poor air circulation
- High humidity (leaf wetness is not necessary, but high humidity is)
- Air temperatures between 60 to 70 degrees Fahrenheit
- Excessive nitrogen fertilizer
How to get rid of powdery mildew on your 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 and DIY-friendly. It only requires a few changes to your lawn care routine, including:
- Decrease shade in affected areas by trimming or pruning plants blocking sunlight.
- Remove, transplant, or trim plants 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 your lawn infrequently and for long periods.
- Avoid heavy nitrogen applications. Conduct a soil test to help you choose the appropriate fertilizer for your lawn.
- Apply fungicides if you cannot modify your turf’s environment. The Clemson Cooperative Extension recommends fungicides containing myclobutanil, propiconazole, or triadimefon to counteract this lawn disease. Always use fungicides according to the product label.
How to prevent powdery mildew on your lawn
Once you remove powdery mildew from your yard, follow these preventative measures to keep the disease away for good:
- Overseed shady areas with a mildew-resistant, cool-season Kentucky bluegrass cultivar and shade-tolerant grass such as fine fescue.
- Prune and trim landscape plants to decrease shade and ensure good air circulation in your yard.
- Maintain proper watering techniques by watering deeply, infrequently, and early in the day.
- Test your soil and develop a suitable fertilization regime for your lawn.
- Leave space between plants to ensure they don’t inhibit airflow or sunlight.
The best way to prevent any lawn disease or fungus is proper maintenance. Lawn fungus like powdery mildew disease thrives in lawns with poor maintenance conditions, such as excess thatch, incorrect mowing habits, leaf piles, wet grass, excessive mulch, and weak root systems.
The healthier your turf, the more resistant it will be against turfgrass disease. Keep up with beneficial lawn treatments to keep your grass healthy and robust.
FAQ about how to get rid of powdery mildew on your lawn
Will powdery mildew kill my turfgrass?
Powdery mildew is not a severe turfgrass disease and generally does not kill turfgrass. However, if you ignore powdery mildew for too long, the weakening turf may succumb to other stressors and die. You can revive your dead lawn with some TLC, but you’ll save yourself time and money if you prevent the problem in the first place.
How does powdery mildew spread?
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 layers, powdery mildew overwinters in living grass tissue. The disease produces spores in the spring that the wind spreads to healthy grass blades.
What time of year does powdery mildew appear?
Powdery mildew appears most often in the spring and fall because of the high relative humidity and warmth. However, it can show up in the summer and winter.
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
What if I can’t identify the fungus on my lawn?
Correctly identifying the fungus infecting your lawn is essential for effective disease control. The control methods that may eliminate 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, contact a local diagnostic lab or turfgrass pathology lab for help. These labs specialize in accurately diagnosing infected turf and are typically located at colleges and 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 quickly, hire a local lawn care professional to handle the job.
Not only can professionals 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’ll spend it doing what you enjoy (or helping the little red hen bake her bread).
Main Photo Credit: Dmitry Brant | Wikimedia Commons | CC BY-SA 4.0
