How to Get Rid of Powdery Mildew on Houseplants—and Prevent It From Returning

If a white, dusty coating suddenly appears on your houseplant’s leaves, don’t panic—but don’t ignore it. “Powdery mildew is a type of fungal infection that affects plants,” says Bex Claire Hamell, houseplant educator and award-winning horticulturist. “It's a challenge for houseplant owners because it can spread easily."

The more it spreads, the more powdery mildew inhibits photosynthesis, which can cause yellowing leaves, leaf curling, stunted growth, and eventual plant death.

Fortunately, with quick action and the right treatment, you can stop the fungus before it overtakes your plants—and prevent it from returning.

Catch It Early

The sooner you identify powdery mildew, the easier it is to control, Hamell says.

Watch for white or light gray powder developing on leaves. It typically begins as small, round spots, but it can eventually cover the entire leaf. 

Certain houseplants are more vulnerable than others. “In my experience, begonias are the houseplant most susceptible to powdery mildew, though I've seen it affect African violets and kalanchoe as well,” adds Hamell.

Remove Infected Foliage

Act quickly to contain powdery mildew at the first sign. “Even with the best practices, [it] can occasionally show up,” says Hamell. “When it does, I try to remove and dispose of any foliage that's visibly infected as quickly as possible.”

Immediately move infected plants away from others and prune infected leaves to reduce the chance of spores spreading. Sanitize pruning tools afterward to avoid unintentionally transferring spores elsewhere.

After pruning, treat the affected plant—and consider treating neighboring plants as well—to further reduce risk. 

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Treat With Sulfur

“My go-to treatment is sulfur, which can treat active cases of powdery mildew, as well as prevent future infection,” Hamell says. 

When used as directed, sulfur “carries a lower risk of toxicity to plants, people, and pets than most other chemical fungicides,” they say—it's available in powder, concentrate, and ready-mixed spray forms. 

To protect foliage, keep treated plants out of direct sunlight or temperatures above 90 degrees Fahrenheit, and avoid combining sulfur with horticultural oils. Reapply periodically on new growth, but you don’t need to re-treat areas unless the product washes off. 

The main downside? It leaves a visible residue and may initially smell slightly like onions—however, the scent fades quickly. Also, because sulfur also has insecticidal properties, make sure to keep it away from beneficial bugs.

Try Neem Oil

Another effective, natural option is neem oil, a pesticide made from neem tree seeds with both fungicidal and insecticidal properties. However, apply it with a bit more caution. According to Hamell, it “does seem to carry a higher risk of damaging sensitive foliage.”

After applying neem oil, keep plants out of direct sunlight and away from temperatures above 80 degrees Fahrenheit to reduce the chance of leaf damage. 

As for the smell? “Some people hate it—I've heard it compared to old peanut butter—but it reminds me of oil paint, which I don't mind,” Hamell says.

Skip Unproven Home Remedies

DIY solutions aren’t always effective. “I frequently see people recommend baking soda, but there isn't much evidence that it treats powdery mildew,” Hamell says. 

While it may offer mild preventative benefits, it won’t eliminate an active infection. Biofungicides are a stronger choice. 

Milk treatments are another popular suggestion—but not one Hamell supports: “I have heard about using milk, but that just sounds gross to me, and potentially smellier than sulfur or neem!”

Prevention

When it comes to powdery mildew, prevention is your best defense. Start by creating an environment where fungus is less likely to thrive. To do this:

• Provide adequate light.
• Maintain good airflow and leave space between plants.
• Water near the top of the soil rather than overhead to avoid splashing spores.

Consistency matters, too—plants may become more susceptible if you miss a few waterings, so keep them hydrated, but not soggy.

Don’t forget to monitor outdoor plants as well, Hamell says. Many susceptible houseplants have close relatives grown outdoors that can serve as reservoirs for spores. 

For extra protection, consider applying a biofungicide. These products use naturally occurring bacteria and fungi that “can outcompete or attack the fungi that cause plant diseases, kind of like a probiotic for plants,” Hamell says. They carry a low risk when used as directed.