You step out of the house one day to check out your lush, green lawn and find what looks to be white or greyish powder covering the tips of your grass. It gets worse over time, eventually taking over large segments of your yard.
There’s no one pranking you by dumping talc powder on your grass. Instead, you likely have a case of powdery lawn mildew, a potentially deadly fungal disease.
Below, we’ll cover the symptoms of powdery lawn mildew, what causes it, and how to treat it.
Symptoms of Powdery Lawn Mildew
As mentioned above, the telltale sign of powdery lawn mildew is a white or greyish, powder- or cobweb-like substance covering the tips of your grass. The sections generally start relatively small, but it spreads quickly, eventually taking over large areas or even your entire yard.
Up close, the grass almost looks as if someone dusted it with talc powder or flour. In severe cases, the grass may turn a dull white, pale green, or yellow.
Powdery Lawn Mildew Causes
The fungus Erysiphe graminis, an obligate parasite that survives only on living grass, causes powdery lawn mildew. The fungus thrives in areas where the humidity is high and temperatures are between 60 and 70 degrees Fahrenheit. This fungus also thrives in the shade, like under a tree or bush.
The powdery look is not the fungus itself. Instead, the powder-like look is from the fungus’ conidia, the asexual spores that allow it to spread. The conidia spread via wind, and the fungal infection can occur just two hours after the spores contact healthy grass.
After infection, the fungus’ haustoria, sucker-like structures, penetrate the grass and absorb nutrients from the outer leaf cells.
How to Treat Powdery Lawn Mildew
Like many fungi, powdery lawn mildew looks tough, but it’s relatively simple to rectify using chemicals or making a few cultural changes.
Regardless of which method you choose, you must start treatment while the grass is still alive. Attempting to treat severe cases — when the grass is yellowing and wilting — will kill the fungus but likely won’t revive your turf.
Treating Powdery Lawn Mildew With Chemicals
The quickest way to rid your lawn of powdery mildew is with chemical treatments. There are various fungicides available that attack the fungus and rid your lawn of the spores causing the powdery look.
Just because you decide to go the chemical route, doesn’t mean you have to resort to potentially deadly lawn treatments. There are plenty of organic treatments available in stores.
When applying treatment, treat well beyond the affected area to prevent the spores from spreading to healthy grass while waiting for the fungus to die.
Treating Powdery Lawn Mildew Without Chemicals
If you prefer to go the nonchemical route, you can use various cultural practices to eliminate powdery lawn mildew. It may take longer to see improvements, but these can also be longer-lasting cures.
Increase the Light
The fungus behind powdery lawn mildew prefers the dark, so increasing the amount of sunlight hitting the affected area may eliminate it. Of course, you cannot lasso the sun and hold it over the area, but you can prune any trees or bushes creating the shade that powdery lawn mildew loves so much.
In areas where you can’t increase sun coverage, like the shady side of a building, you may want to choose more fungi-resistant turf, like fine fescue or rough bluegrass.
Reduce the Moisture
Erysiphe graminis also loves humidity, so reducing the moisture and improving the airflow in the area can help. You can achieve this by again pruning trees and bushes around the affected area.
You can also lower the humidity by adjusting the watering schedule and amount in that area.
Return to Green
Powdery lawn mildew may look like a horrific death sentence for your yard, but the treatment is pretty simple. Plus, if you time your treatment correctly, you can swiftly eliminate the fungus and bring the green back to your grass. With timing of the essence, now’s the time to get started.