How to Treat a Houseplant with Powdery Mildew

Powdery mildew is a common fungal disease that can infect a wide variety of houseplants. It appears as a white or gray powdery coating on leaves, stems, and flowers. Powdery mildew can weaken plants and reduce their aesthetic appeal, but it is rarely fatal.

How to Identify Powdery Mildew

The most common symptom of powdery mildew is a white or gray powdery coating on leaves, stems, and flowers. The coating may be difficult to see at first, but it will become more obvious as the disease progresses. Powdery mildew can also cause leaves to curl, yellow, and drop off.

Causes of Powdery Mildew

Powdery mildew is caused by a fungus that thrives in cool, humid conditions. It is most common in the winter and early spring, when indoor humidity levels are high. Powdery mildew can also be caused by overcrowding plants, poor air circulation, or overwatering.

How to Treat Powdery Mildew on Houseplants
Closeup of Powdery mildew

Treating Indoor Plants with Powdery Mildew

There are a number of ways to treat powdery mildew on houseplants. The easiest method is with a household solution of baking soda, water, and liquid soap.

Treating Powdery Mildew on Houseplants
Powdery mildew on a Jade Plant.

Baking Soda Solution to Treat Powdery Mildew

This baking soda solution is a safe and effective way to treat powdery mildew on houseplants. It is also inexpensive and easy to make.


  • 1 tablespoon baking soda
  • 1 gallon water
  • 1/2 teaspoon liquid soap (such as Castile soap)


  1. Mix all of the ingredients together in a spray bottle.
  2. Spray the affected plant thoroughly, including the underside of the leaves.
  3. Reapply the spray every few days until the powdery mildew is gone.


  • Be sure to test the spray on a small area of the plant before applying it to the entire plant. This is to make sure that the plant is not sensitive to the baking soda solution.
  • Avoid spraying the plant in direct sunlight.
  • Do not water the plant for 24 hours after spraying it with the baking soda solution.

Other Ways to Treat Powdery Mildew

Here are a few other common methods:

  • Remove infected leaves: If the infection is mild, you can simply remove the infected leaves. Be sure to dispose of the leaves in a sealed bag to prevent the spread of the disease.
  • Use a neem oil solution: Mix one teaspoon of neem oil with one quart of water and spray the solution on the affected plant. Be sure to spray the underside of the leaves as well. Repeat the application every week until the powdery mildew is gone.
  • Use a commercial fungicide: There are a number of commercial fungicides available through Amazon or your local garden center that can be used to treat powdery mildew. Be sure to follow the instructions on the product label carefully.
Treating powdery mildew
Treating powdery mildew on a zucchini leaf.

How to Prevent Powdery Mildew

The best way to prevent powdery mildew is to create a growing environment that is unfavorable to the fungus. Here are a few tips:

  • Provide good air circulation: Powdery mildew thrives in still air, so it is important to provide good air circulation around your houseplants. You can do this by opening windows and doors, or by using a fan.
  • Avoid overwatering: Powdery mildew also thrives in humid conditions, so it is important to avoid overwatering your houseplants. Allow the soil to dry out slightly between waterings.
  • Space plants out: Avoid overcrowding your houseplants. This will help to improve air circulation and reduce the humidity around the plants.
  • Inspect your plants regularly: Inspect your plants regularly for signs of powdery mildew. If you see any signs of the disease, treat it immediately to prevent it from spreading.
Houseplants with Powdery Mildew
Detail of powdery mildew

Related Article: Humidity and Houseplants

If you have further concerns about powdery mildew on your houseplants, you may want to consult with a local nursery or garden center.

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