Houseplant disease can make the most beautiful indoor plants look ragged, spindly, discolored and downright unhealthy. Although it may be difficult to decipher exactly what causes the leaves on houseplants to turn colors and fall off, restoring the health of these plants is not too difficult, especially if the problem is caught early on. Usually with just a little extra care and a few adjustments, the green foliage and health of houseplants can be restored and their beauty can be brought back into the home.
Often the exact conditions houseplants need to survive are the factors that permit the onset of disease. Adverse growing conditions cause plants to become stressed and susceptible to not only disease but pests as well. Some factors that contribute to plant stress include: over-watering or under-watering; too much or too little of a nutrient; direct sunlight or light that is too low; air temperature and circulation; poor drainage; and even transplant shock. Even something as simple as moving the plant to a different location in the home can cause stress.
Houseplant diseases can be classified into three basic types: fungal, bacterial and abiotic. Fungal spores and microscopic organisms called bacteria tend to spread and multiply in conditions of "high humidity, crowding and poor air circulation around plants," according to the University of Minnesota Extension website. Abiotic diseases are directly caused by inhospitable conditions. If stress does not make the plants vulnerable to fungal or bacterial disease, abiotic disease will set in simply due to poor growing conditions.
While the symptoms of bacterial and abiotic diseases make them difficult to diagnose, fungal disease in houseplants are fairly easy to spot. White powder on the foliage; dark, spongy plant roots; leaf spots that are black with a yellow ring around them; and stems with a soft, black ring near the soil line are generally symptoms of a fungal disease. Bacterial infections typically result in light green or translucent spots on the leaves; yellowing of new leaves; lesions on foliage; and yellowing of the leaf margin. Yellowing leaves is also a symptom of abiotic diseases, along with spindly plant growth, brown leaf tips and few flower blossoms.
Most often with the onset of a disease, the houseplant is still salvageable if immediate measures are taken. The infected area of the plant needs to be pruned first, including any black, mushy roots. Next, adequate conditions for healthy growth need to be provided. Re-pot the plant if infected soil is suspected and re-pot every six months to one year with sterile soil. Avoid wetting the foliage of diseased plants as this tends to aggravate many fungal diseases. And, last but not least, sterilize. Avoid touching infected plant parts when possible and always disinfect tools used on diseased plants to avoid further contamination.
Preventing plant disease in the home begins with inspecting for infections and signs of stress when purchasing new plants; healthy plants are less likely to spread disease to already existing plants. Also, provide the right environment for healthy plant growth. Low humidity, proper air circulation and drainage, and keeping plants on a watering schedule are ways to properly care for houseplants. As with most diseases, preventing the onset of them is the best cure.
- Government of Alberta: Agriculture and Rural Development; "House Plants: Diseases"; Oct. 22, 2007
- Pennsylvania State College of Agricultural Sciences Cooperative Extension; Department of Horticulture Fact Sheet;"Preventing, Diagnosing and Correcting Common Houseplant Problems
- University of Minnesota Extension; Bacterial Leaf Diseases of Foliage Plants;F.L. Pfleger and S.L. Gould