Houseplants breathe life into dark, dull rooms, bringing beauty and warmth into a home’s décor. That beauty, however, can quickly fade if your indoor garden falls victim to disease.
Leaf spot is a treatable fungal disease.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Mosaic virus —viral infected plants should be removed from the house and destroyed to avoid spreading the disease. They are not treatable and oftentimes fatal.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Bacterial wilt, a treatable but difficult-to-control disease, may also contaminate the plant’s soil.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Houseplant diseases fall into two main categories: fungal and viral. Most commonly, plants suffer from fungal diseases resulting from mildews, molds and other related organisms, and the problem is curable. Viral diseases, on the other hand, are more sinister. They’re usually incurable, sometimes contagious, affect a plant’s vigor and bloom, and can kill a plant outright. (Bacterial infections are another source of houseplant diseases, but they’re rarer than the other types.)
Although a variety of fungal diseases exist, all cause plants to mold or rot. They generally result from overwatering or root suffocation, accompanying compacted soil that lacks sufficient airspace. Common signs of fungal disease include foliage loss, stunted growth and droopy leaves. Unfortunately, it’s easy to mistake wilting as a sign of thirst instead of a fungal disease, so infected plants tend to get watered more, exacerbating the problem. In extreme cases, the roots deteriorate, the plant develops fungal infections, and it eventually weakens and dies. Crown or stem rot is similar: The plant wilts or turns brown, and the plant’s stem or trunk becomes soft and discolored near its base.
Fungal diseases can be cured by cutting back on watering and then watering only when the soil nears complete dryness. It’s also important to keep your plants out of standing water and keep the soil loose so that sufficient air can reach the roots. (Elevate plants to allow air penetration to the roots if possible.) It may be necessary to also repot the plant in a well-draining mix, removing as much of the old soil as possible. Two fungal conditions commonly occur on foliage: leaf spot and powdery mildew.
Viruses are the other main form of houseplant diseases. These microscopic organisms generally affect a certain group of plant species or families. Signs of infection include a lack of vigor, yellow streaking or mottling, and stunted or disfigured growth.
Plant viruses are incurable, so it’s best to destroy the infected houseplant. Before resorting to this course of action, however, isolate the plant and give it proper care to rule out other causes or to see if it will recover after all. The good news is that plant viruses are unlikely to spread widely among all of your houseplants. That said, insects like aphids, mites and scales often carry viruses, so prompt control of pests is a good step toward prevention. Human touch and gardening tools can also spread plant viruses, so be sure to thoroughly wash hands and tools before and after touching your houseplants.
The following quick reference lists some common houseplant disease symptoms you may notice on your plants, as well as possible causes and remedies.
Symptom: Brown stains and softened tissue near base of stem or crown of plant; leaves may yellow or drop.
Cause: Crown or stem rot; usually associated with keeping soil overly moist. (Also look for decaying stems.)
Remedies: Rarely curable; remove infected foliage, dipping pruning shears in rubbing alcohol solution between cuts. Reduce watering the plant. Repot in a soil-free, well-drained mix. Root cuttings of healthy growth.
Symptom: Soft brown spots on leaves; powdery black or brown dusting on foliage and blossoms; leaves may drop.
Cause: Leaf spot – fungal disease; common in low-light, crowded plantings. The condition usually results from an environment that’s too warm, too humid or poorly ventilated.
Remedies: Remove and dispose of infected leaves and shading foliage; increase air circulation; apply sulfur spray or powder – an organic fungicide. (Completely read and carefully follow all package instructions exactly when applying any fungicides.)
Symptom: Gray or white, light powdery dusting on leaves, stems and flower buds; deformed new growth; stunting, loss of vigor. Leaves may also curl.
Cause: Powdery mildew – fungal disease; common if humid, warm days and cool nights alternate.
Remedies: Remove and dispose of infected plant parts; increase air circulation; spray affected plants with a solution of 1 tablespoon baking soda and 3 tablespoons horticultural oil to 1 gallon water; dust with sulfur. Move the plant to a location with better ventilation, cooler temperatures and less humidity. Water carefully and avoid overly wet soil.
Under the proper care and environmental conditions, your indoor garden can thrive for years. But that care doesn’t end with simply providing the appropriate amount of water, sunlight and fertilizer. Keeping a constant eye out for – and properly identifying – houseplant diseases and pests will go a long way in maintaining the beauty of your living décor.
