House Plant Diseases

Discover how to identify, prevent and treat common house plant diseases, such as gray mold, bacterial leaf spot, sooty mold, and other types of house plant fungus.


Botrytis blight -- better known as gray mold -- is one of the more common afflictions of house plants. This fluffy, gray mold is a fungus that feeds on dying plant tissue. It usually enters a broken stem or leaf, then quickly spreads to the rest of the plant. This fungus prefers damp, dark, cool conditions and tends to thrive more in a greenhouse than a home. Soggy soil and lack of air circulation also invite trouble.

Remedy: Cut off infected parts, as well as any dead leaves and flowers. You can prevent this fuzzy gray mold by routinely inspecting plants and pruning off dead stems and flowers as soon as you notice them. Treat your house plant with a fungicide, such as 3-in-1 Insecticide/Fungicide/Miticide. It kills fungus as well as many common insects and other house plant diseases.

Powdery Mildew

Powdery mildew is a disease that appears as a white, dusty powder on foliage. It prefers warm temperatures and dry conditions. Good air circulation helps to prevent infestation.

Remedy: Prune off affected leaves. Get help for identifying and treating powdery mildew here.

House Plant Diseases Prevention Tips:

  • Air circulation around your plant will help prevent spread of any fungus.
  • Wiping dust off leaves not only makes them more attractive, it helps leaves to take in air and sunlight. And that makes it healthier, less prone to house plant diseases and bugs.
  • Clean your pruning shears to avoid transferring diseases from one plant to the next.


Rust looks like brown spots that form on the tops of leaves, with brown rings on their undersides. Rust fungus thrives in a wet environment, making overwatered plants a target. Pelargoniums (commonly known as geraniums) are a favorite of rust disease.

Remedy: Cut off affected leaves. Treat with a Sulfur Plant Fungicide.

Bacterial Leaf Spot

Bacterial leaf spot is caused by a fungus and shows up on leaves as a sunken dark spot. Wet leaves contribute to leaf spot. When watering your house plants, don't get water on the leaves because water takes a long time to evaporate indoors.

Remedy: Cut off affected leaves to remove the fungus from the plant and to prevent it from spreading to nearby plants. 3-in-1 Insecticide/Fungicide/Miticide is an eco-friendly solution for controlling this fungus and other house plant diseases.

Damping Off

Damping off disease affects seedlings. Unfortunately, all you'll notice are seedlings that suddenly fall over and die. This fungus spreads quickly, wiping out whole trays of seedlings in a short time.

Remedy: Take a look at these tips for identifying and preventing damping off disease.

Sooty Mold

Sooty mold isn't actually a disease. This black, dirty-looking mold grows on leaves covered by the honeydew excreted by sap-sucking insects, such as scale, white flies and aphids.

Remedy: Fortunately, it's easy to wash off. Just wipe the leaves with cloth dipped in lukewarm, soapy water. Sooty mold will come back, however, unless the pests are controlled.

Safety Tips:

Follow directions carefully before using any fungicide or insecticide. Remember, they are not all-purpose products. Look for your specific plant on the label. If your plant isn't mentioned, don't use it.

Always spray fungicides outdoors. Avoid inhaling the fumes. Wear goggles and a mask when spraying any chemicals. Take these precautions even for products labeled organic -- even "natural" solutions are dangerous.

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