Indoor tropical plants can be susceptible to infestation by a variety of sap-sucking insects, particularly if the plants are summered outdoors. Insects may be brought indoors with the plants at season's end. Another source of infestation is newly purchased greenhouse plants, which should be isolated from your other indoor plants for two to three weeks to ascertain whether or not they are infested with these pests. Inspect your indoor tropical plants frequently; pests are much easier to control or eradicate if caught before their populations grow too large.
Several species of scale attack houseplants. They are crawling insects that develop a hard, scaly back under which eggs are laid and then hatch. The protective body of scale protects the insects from insecticides and makes it difficult to eradicate them. However, young newly hatched scale insects move away from the mother to feed and are susceptible to eradication by insecticides at this time. To be effective, spray with horticultural oil weekly or twice weekly for two to four months, which encompasses their life cycle and gives the greatest chance of elimination.
Symptoms of spider mites on indoor tropical plants include small wounds on the underside of the leaves and stems which resemble white flecks. As spider mite damage progresses, the leaves become discolored and appear to be graying or bronzing. Plants that are infected with large populations of spider mites may have visible webbing accompanied by premature leaf drop. Spider mites are hard to control; the most effective method is simply washing the plant daily with a strong spray of water from the shower or kitchen sprayer. Several weeks of this daily washing will reduce populations considerably. Horticultural oil sprays are the most effective pesticide for controlling spider mites. Heavily infested plants may need to be disposed of.
Aphids are tiny insects that suck sap from the plants and excrete a sticky substance, along with causing distorted new growth and wilting of existing growth. Some varieties of aphids are resistant to insecticides due to overexposure in greenhouses, but many aphid varieties can be effectively controlled with insecticide sprays. The most effective treatment is consistent washing of the plant with a strong spray of water along with periodic spraying with insecticidal spray.
These sap-sucking insects have soft bodies and excrete large amounts of a sticky substance referred to as “honeydew.” Mealybugs primarily attack the roots, but are usually visible on the foliage as well. The females produce a cottony-like material on which to lay eggs. The appearance of this cottony-like material and leaf drop are two signs that your plant may be infected with mealybugs. Spray with 50 percent alcohol-water solution, insecticidal soaps or commercially available pyrethroid insecticides, following the manufacturer's instructions.