Powdery Mildew on House Plants

How to Identify Powdery Mildew Disease

It's a fungus that looks like white powdery patches on leaves, stems, or flowers that later turns grayish brown. These are the usual causes:

  • High humidity
  • Low light
  • Poor air circulation

The powdery patches are fungal spores and they multiply rapidly. You'll usually notice the mildew first on the top surface of older leaves. By this time, the disease has been inside the plant a week or longer. The affected leaves may turn yellow or brown and eventually fall off.

African violets and begonias are often susceptible because they prefer the high humidity that is ideal for fungus growth.

powdery mildew, powdery mildew on plant leafDry, white powdery patches on leaves are a symptom of powdery mildew.

Treatment for Powdery Mildew

The easiest way to control the spread of this fungus is to cut off all the affected leaves and give the plant more light.

Move the plant away from other plants to improve air circulation and to prevent the spread of fungal spores.

You've probably heard of using baking soda as a treatment. This works well for prevention, but does not cure an affected plant. If you want to try this solution as a preventative measure, spray the plant with a mixture of 1 tablespoon of baking soda dissolved in 1 gallon of water.

Safer Brand 3-in-1 Ready-to-Use Garden Spray

Spray the affected areas with fungicide made for house plants. The 3-in-1 Insecticide/Fungicide/Miticide (shown here) works to control powdery mildew and other types of fungus and insects. Read the label carefully and follow the manufacturer's directions for use.

Prevention Tips

  • Keep it clean. Fungal spores can easily be carried on your hands and tools from one plant to another. It's a good idea to wash your hands and sterilize your tools after contact with affected plants to avoid spreading the fungus around.
  • Water your house plants regularly. Plants are most affected by this disease when roots dry out and foliage is moist.
  • Give them air. Although tropical houseplants need humidity to thrive, some need more air circulation than others. Plants that are epiphytes in the wild (they grow on trees), such as bromeliads, tillandsias, and most orchids, are healthier with good air flow. And as I mentioned before, thickly leafed African violets and begonias are also susceptible to fungus. A low-speed fan can help, if powdery mildew becomes a problem.

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