Why Is My Tropical Plant Getting White Spots?

Mealy Bugs

• Mealy bugs are soft-bodied insects that feed by inserting their mouth parts into leaves and stems and sucking out sap. They are grayish and covered in a white, waxy substance that looks like cotton. They are largely immobile and can look like fuzzy white spots all over your plant. Systemic insecticides applied to the soil can help control mealy bugs. Washing plants with a solution of 1 to 2 tsp. of dish soap to 1 gallon of water can also be effective.

Scale

• Scales are immobile, sap-feeding insects that can cause distorted leaves, yellowing and even leaf drop. When immature scales find a place to feed, they anchor themselves with their mouth parts and cover themselves in a hard armor that can be black, gray, white or brown. Scales are tiny, and on your plant they may look like scabby white spots. Spray insecticides target immature scales, and systemic insecticides can help control adults. Washing plants with a solution of 1 to 2 tsp. of dish soap per 1 gallon of water is also helpful.

Spider Mites

• Members of the arachnid family, these spider-like pests are not uncommon on houseplants. They feed by sucking the sap out of leaves and can cause a fine white stippling on heavily infested leaves. They may also leave a fine webbing on your plants. Dip or spray your plants with insecticides, or apply a systemic insecticide to the soil. Washing plants with a solution of 1 to 2 tsp. of dish soap to 1 gallon of water can also help. Some species of predatory mites may also be available at your local garden center.

Environmental Factors and Disease

• Several environmental factors in your home can cause leaf spots. Aerosol sprays, hot kitchen grease and even cold water can cause leaf spotting. Cold water is particularly troubling to African violets and the Central American native, gloxinia. Disease is rare in houseplants, according to North Dakota State University, because the indoor environment is too dry. However, white spots on your leaves could be caused by a fungus called powdery mildew. This fungus appears as a white, powdery dust on leaves, stems, buds and flowers. If you suspect powdery mildew is the cause, refrain from misting leaves, as this can further spread the pathogen. Destroy all infected plant parts, and apply a fungicide.