NC Cooperative Extension Service

INDOOR PLANT PESTS
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Prevent Pest Infestations

Most newly purchased plants are healthy, but sometimes a plant may have a very low number of insects or mites. Many indoor gardeners isolate new plants for about 10 days before grouping them with others. This reduces the potential for problems in your other plants, should symptoms appear on the new plant. back to the list

What's Wrong With My Plant?

Your job is a little easier if you are seeing strange insects on your plant. Catch a few of the insects and have them identified. Unfortunately, often the indoor gardener first notices signs of plant stress, such as leaf drop, spots on the leaves, or a change in leaf color, without finding any insects. These symptoms may or may not indicate an insect problem. Other problems that can cause plant stress include over- or under-watering, soil fertility imbalances, improper lighting, temperature, or humidity. For the sake of brevity, we will assume you have caught and identified the insect that is causing your problem. back to the list

Mealy Bugs & Scale

Mealy bugs and scale feed on the plant sap from leaves and stems. While scale infections grow slowly, mealy bugs multiply rapidly.

Mealy bugs have small soft white or pink bodies. In addition, they secrete a fluffy white wax which makes the plant leaf or stem look as if tiny bits of cotton are stuck to it. Infected leaves may be covered with small white spots. Leaves will fall off of the plant, black sooty mold may grow, and eventually the plant may die. In the meantime it is unsightly and a risk to healthy plants.

Isolate any infected plant immediately. Destroy heavily infected plants. Spray a mixture of alcohol and water directly onto the mealy bugs if there are a large number of them. If only a few mealy bugs are seen, dip a cotton swab in alcohol and dab the insects to remove the waxy coating that protects them. Then spray the plant with a foliar spray or a root systemic insecticide. Repeat these steps at weekly intervals until no more mealy bugs are seen. Be sure the pesticide is designed for indoor plants and follow all pesticide directions carefully.

Scale are harder to find on a plant. Many look like little bumps on the plant, and you may not realize they are not part of the plant itself. They tend to cluster together on twigs and leaf midveins. Infected plants may develop spotted leaves, branch dieback, and leaf drop. Many scale insects excrete a sticky liquid onto the plant surface, which forms an ideal place for mold to grow. Often this mold is black and sooty in appearance.

Isolate and destroy heavily infected plants. Because scale spreads more slowly, foliar or root pesticides are applied at 2 to 3 week intervals rather than weekly. Prune infested branches, hose off crawling scale with water, and improve the plant vigor by increasing the amount of light and by improving root health. back to the list

Mites

Two common types of mites on indoor plants include spider mites and eriophyid mites. Spider mites pierce the plant leaf to extract sap, causing tiny yellow spots on infected leaves. Many spider mites are tiny red mites which are difficult to see without a magnifying glass. Infested plants will develop a bronzed look. The leaves of mite-infested plants eventually turn brown and fall off. As mites multiply, the entire plant may turn yellow, drop leaves, and eventually the plant dies. Spider mites also spin small webbing on shoot tips and leaf axils.

Eriophyid mites damage leaf buds. The new leaves and flowers will be discolored and misshapen. Small brown specks on new leaves are the first indication of an Eriophyid mite infestation. Plants become stunted and misshapen, but usually do not die from this type of mite. Since these mites are extremely tiny, almost transparent in color, and hide in buds, they are very difficult to find even with a magnifying glass.

Mites are very difficult to control. Destroy heavily infected plants. Increase humidity of the remaining plants' environment, keep infested plants moderately moist at all times, and filter the sunlight falling on infested plants with filmy curtains. Apply less fertilizer. Spray plants weekly with a weak soapy water solution to prevent reinfestation. Foliar miticides should be applied at 7 to 10 day intervals. Be sure the miticide is designed for indoor plants; follow all pesticide directions carefully. back to the list

Whiteflies

Plants infested with whiteflies become yellow and sickly. The leaves show cupping and slower growth. When an infected plant is brushed or moved, the winged adults are easily seen as they fly around. They resemble tiny winged moths.

Destroy infected plants. Use yellow sticky traps to reduce whitefly numbers. Since whiteflies are highly resistant to pesticides, select non-susceptible plant species for use in cooler sites. back to the list

Aphids

Aphids cluster at the end of new shoots on flower buds, and on the undersides of leaves. Aphids may be light green, red or black in color. All aphids feed on plant juices, and cause stunted, distorted leaves and unthrifty plants that grow slowly. Many aphids are resistant to pesticides. To control a very mild infestation, spray warm soapy water directly on the insects, and then remove the soap with plain water. Destroy heavily infested plants. back to the list

Thrips

Thrips are tiny insects which cause silvery or white spots or streaks on leaves. Infected leaf or flower buds will emerge disfigured and damaged. Since thrips are extremely tiny, crawl quickly to dark protected areas of the plant when disturbed, and hide in buds, they are very difficult to find even with a magnifying glass. However, thrips are attracted to yellow. Yellow cards coated with a sticky oil can be placed near a suspected infestation. If thrips are present, they will become trapped on the cards.

Mist plants every few days to wash off adult and larvae thrips, or apply foliar pesticides every five days. Many pesticides are effective against thrips. Be sure the pesticide is designed for indoor plants and follow all pesticide directions carefully. back to the list

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