Each time you water your houseplants, touch and examine them for early symptoms of ailments. If you notice a problem with one plant, isolate it from other plants to avoid spreading of the disease or pests. Next, diagnose the problem in order to start treatment. Most plant ailments are treatable.
Two of the most common insect problems occur with scale insects and aphids. The damage from scale insects appears as leaf yellowing, leaf drop, and sticky residue on the leaves. Apply horticulture oil, which smothers the adult insects. Aphids also leave a sticky residue. You can easily control aphids with insecticidal soap or horticultural oil.
Fungal Leaf Spot
Fungal leaf spot appears on leaves as circular reddish brown spots surrounded by yellow. Clip off the affected leaves, and water your plants carefully to avoid splashing among the leaves, which spreads the disease. The spotting, although unsightly, is not harmful to the point of destroying the plant.
Root or Crown Rot
Root or crown rot develops from the plant sitting in soggy soil or standing water. Dry out the plant and re-pot it, but first prune off damaged and diseased roots.
Botrytis, an airborne fungal disease, affects a wide range of plants and spreads quickly. It appears as light brown patches on leaves, stems or flowers and darkens, turning into a soft, grayish mold. Humidity causes this condition. Remove affected parts of the plant and treat with a fungicide or fungicidal soap. Improve air circulation around the plant.
Powdery mildew appears as white or grayish powdery patches on leaves, stems, and flowers. Remove affected leaves and spray the plant with a fungicidal soap. Provide more light and adequate air circulation for the plant.