Houseplant Pest Identification

Spider mites (Tetranychus urticae) are tiny arachnids that pierce leaf cells and feed on the contents, leaving a stippled or sandblasted look on foliage. Webbing along leaf undersides is a tell-tale sign of an established infestation. They thrive in warm, dry conditions — typical indoor air in winter.

Mealybugs are soft-bodied sucking insects covered in a white waxy coating that looks like cotton tufts. They cluster in leaf axils, along stems, and at the base of the plant. Untreated infestations weaken the plant and produce sticky honeydew that attracts sooty mold.

Fungus gnats are small dark flies (~2 mm) whose larvae live in the top 2–3 cm of moist potting media, feeding on organic matter and fine roots. The adults are mostly a nuisance; the larvae can damage seedlings and stressed plants. They indicate consistently overwet soil.

Scale insects are armored or soft-bodied sucking pests that attach to stems and leaves and feed on plant sap. Adults look like small brown or tan bumps and don’t move once settled. Heavy infestations weaken the plant and produce honeydew that attracts sooty mold.

Thrips are slender insects (1–2 mm) that rasp leaf surfaces and suck out the contents, leaving silvery streaks, deformed new growth, and black fecal specks. They breed quickly and are commonly introduced on new plants.

Aphids are small pear-shaped soft-bodied insects that cluster on new growth and the undersides of leaves, sucking sap and excreting honeydew. They reproduce rapidly indoors and can transmit plant viruses, but are also the easiest of the common pests to knock back.