A succulent plant, kalanchoe produces large, glossy leaves with frilled edges. It provides a profusion of small, four-petaled flowers in a range of colors. Kalanchoe is relatively low-maintenance with few problems when grown as a houseplant, but there are some diseases and insects that can damage the plant if they aren't controlled.
Mildew and Mold
Powdery mildew and other mold problems infect some kalanchoe. Plants grown in cool, overly moist conditions are more prone to these fungi. Powdery mildew produces a fine webbing on the foliage that then develops into mottled, yellow spots. Phytophthora and pythium are two other common fungus problems. Both cause a moldy growth on the foliage and leaf discoloration. Prune out infected leaves and avoid wetting the foliage when irrigating to control minor problems, or apply potassium bicarbonate for more severe mildew infestations.
Overwatering and cool temperatures can cause oedema problems, which occur when plants take up water faster than they can use it. The first symptoms are small, cork-like growth on flowers and leaves. These growths harden and turn to a brown or tan color as the disease progresses. A kalanchoe grown in overly moist, warm soil in a room with cool air and little light is most susceptible to this disease. Avoid overwatering, and provide kalanchoes with the proper light to prevent oedema problems.
Many varieties of kalanchoe are quick-growing, causing them to become unwieldy as indoor houseplants. Quick growth can also lead to leggy, unattractive plants instead of full, bushy plants. Applying a growth retardant, such as B-Nine foliar spray, at the start of winter and two applications in summer prevents elongation of the flower stalk and overgrowth.
Common houseplant insects also infest kalanchoes. Aphids and mealybugs are two common pests. Aphids feed on the underside of leaves but are easily controlled with insecticidal soap applications. Control mealybugs with insecticidal sprays or by swabbing rubbing alcohol directly onto the insects. Scale and whiteflies are other insects that may infest kalanchoes and may be managed either by hand removal or insecticides.