Insect pests can discolor, weaken and eventually kill houseplants. These pests are often small and can go undetected for weeks or months if gardeners don't carefully monitor their plants. Check plant leaves and stems whenever you water or move houseplants and whenever you bring them inside after you've left them outside for a day in the sun.
Mealybugs are small, soft-bodies insects that crawl along the plant parts. They leave a slimy trail of honeydew, often the most notable sign of their presence. These insects prefer jade, cactus, coleus, poinsettia and lantana plants but can infect others as well, according to Colorado State University.
To remove mealybugs from a lightly infested plant, swab its leaves with a cotton ball soaked in rubbing alcohol. For larger infestations, use a spray containing pyrethrin or an insecticidal soap.
The spider mite is the most common houseplant mite pest. Spider mites eat plant sap, leaving behind tiny white dots on plant leaves or stems. With time, plant leaves begin to turn tan or bronze. Hibiscus, fig, dracaena and ivy are among spider mites' preferred plant hosts.
Throw out heavily infected plants, recommends Colorado State University. Remove spider mites from the plant by spraying it with hose water or by applying horticultural oil.
Aphids come in an array of colors, from green to tan or orange. These pests crawl or fly along plant parts. They enjoy hibiscus, chrysanthemums, ornamental peppers, herbs and vegetable plants. Aphids secrete a sticky honeydew that coats leaves and stems. To control aphids, wash the plant under water or spray it with an insecticide containing imidacloprid.
Quarantine New Plants
Bringing new and infected houseplants into the environment is typically the way other houseplants get insect pests. When you purchase new plants, inspect the leaves and stems for signs of infestation and purchase only healthy-looking plants, such as those with bright, clean leaves. Quarantine a newly purchased plant for two to three weeks, keeping it in an isolated environment from other houseplants. If you observe no evidence of pests, release the plant from quarantine.
Other Prevention Tips
Prevention is the best defense against insect pests. The University of Kentucky advises purchasing plants only from nursery dealers, because these plants are most likely to be kept pest-free. When you repot plants, use sterile potting soil rather than yard soil. Wash your hands after handling plants to avoid spreading disease from one to another.