Leaf Spots on Houseplants (5710)

Leaf spots are symptoms of diseases caused by fungi, bacteria, viruses, or nematodes.  Most leaf spots are discrete dead spots on the leaf surface.  If the leaf surface has a white powdery appearance, then the problem may be a disease called powdery mildew.  Under severe disease conditions, the leaf spots may enlarge and run together to form larger spots or turn the entire leaf brown. If the entire leaf or shoot turns brown, the disease is then called a blight.  Fungal, bacterial, and leaf spots caused by nematodes are worse under high humidity or wet conditions since air currents and water will move the pathogens from spot to spot.  Viral diseases are spread by propagation processes or by insect transmission such as aphid feeding.

Disease management:  Always inspect plants carefully before purchase and isolate new plants for several weeks before mixing them with the rest of your collection. Unless you have a greenhouse, leaf spots will not spread rapidly in indoor environments, and pesticides will not be needed for disease management. One of the most practical disease management techniques is to pick off and discard infected leaves. To prevent conditions favorable for disease, avoid prolonged wet conditions caused by practices such as misting or watering your plants in the evening.  Space plants far enough apart to allow good air circulation around the foliage to reduce humidity levels.  If you suspect a viral disease, then the entire plant will have to be discarded.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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