Bugs are not just a problem for outdoor plants. Every time you bring a plant home, you run the risk of tracking in unwanted guests. Once inside, pests can invade all of your other houseplants—especially those that aren't receiving sufficient light, heat, or water. Here are some tips for dealing with the most common houseplant pests:
These soft-bodied insects resemble small tufts of cotton and are almost undetectable in houseplants until they reach full maturity. Mealybugs pierce the stems and leaves of plants to drink their sweet inner sap. The exposed sap in turn attracts other invaders like ants and sooty mold. For this reason, mealybug infestations can distort the growth of new plants. To control an outbreak, try picking the pests off of your houseplant by hand. If you're not particularly interested in picking up insects, you can always get rid of mealybugs by dabbing them with a cotton swab dipped in rubbing alcohol.
Scales use their needle-like mouths to feed on plant sap and secrete a waxy coat that makes them look like brown or gray bumps on plant leaves. These pests are round and only 1/16 to 1/8 of an inch in diameter. A heavy infestation can stunt plant growth and cause leaves to fall off. To control scale bugs, wash your plant's leaves with an insecticidal soap. You might want to try mixing in a few drops of liquid soap to help the insecticide slip beneath the pest’s waxy shell.
These pests multiply rapidly and kill houseplants. Spider mites feed on the undersides of leaves and cause spots of yellow discoloration to appear in their wake. They are quite difficult to see with the naked eye. If you think you have a spider mite problem, try placing a sheet of white paper under a discolored leaf. Tap the leaf and look for any moving specks on the paper. Spider mites love hot, dry conditions and can be deterred by misting your plants regularly. In the event of an infestation, wash your plant's leaves with an insecticidal soap.
Adult thrips are about 1/16 of an inch long and can initially look like dark, thin threads on your houseplant. These pests are known for their mobility and can fly, jump, and run. Thrips tend to scrape the leaves and flowers of plants in order to suck on their inner fluids. Discolored leaves, particularly those marked with irregular, silvery streaks, are the most telling signs of a thrip invasion. Remove the insects by hand and give the leaves a good wash.
You can often spot these small, white or gray insects in the saucer after watering your plant. Springtails feed on decaying roots and fungi and thrive in damp potting soil. Though they rarely damage houseplants, these pests can become a nuisance very quickly. To ward off springtails, keep your soil as dry as possible between waterings.
Surprisingly, these pests are more similar to mealybugs or aphids than they are to actual flies. The tiny, moth-like insects are usually discovered on the undersides of leaves. They feed on plant sap and cause leaves to become discolored and eventually drop. Wash your houseplant's leaves frequently to avoid attracting them. If you ever encounter whiteflies in your plants, remember that flying insects are easily and safely dealt with by using fly paper. Actually, any piece of yellow paper cut into a square and covered with Tanglefoot should do the job.
These spider-like pests feed on young, tender leaves and cause them to blacken. Especially affected leaves may exhibit stunted growth and a brittle texture. Unfortunately, you'll typically have to throw away any plants infested with cyclamen mites.
The larvae of these small flies feed on leaf surfaces and leave behind narrow, white trails. Contaminated plants tend to have a consistently wet appearance. Adult leafminers also lay eggs which resemble small specks. To tame an outbreak of leafminers, remove any damaged leaves from your houseplant and destroy them.
General Pest Control Tips
Before bringing a plant indoors, always be sure to carefully inspect it and its container for any signs of pests. Even if you don't immediately notice anything unusual, you'll want to keep new plants quarantined for about six weeks. During this time, perform weekly pest examinations.
As for the plants you already own: take them out of their pots from time to time and check their soil for insects. When repotting houseplants, avoid taking soil from the outdoors. Opt for an indoor potting mix instead. From here, take the time to wash your smooth-leaf plants with a soft, damp cloth every three to four weeks to discourage infestations. You can rinse large plants in a lukewarm shower. Keep any cut flowers from your garden away from houseplants, and check your doors and window screens for holes to make sure pests aren't getting into your home from the outside.
If you ever stumble upon an unfamiliar pest, be sure to visit the Bug and Insect Identification forum here on Dave's garden.