From spider mites to fungus gnats, here's how to identify the most common houseplant pests and treat them before they spread to the rest of your collection.
Fine, faint webbing on the undersides of leaves or between stems, combined with tiny speckled or stippled discoloration on the leaves themselves, points to spider mites — tiny arachnids that thrive in dry indoor air and multiply quickly. Rinse affected leaves (top and underside) thoroughly under lukewarm water, then apply insecticidal soap or neem oil every 5-7 days for 2-3 weeks. Raising humidity around the plant afterward helps discourage them from coming back.
Small, white, cottony clusters tucked into leaf joints and along stems are mealybugs — slow-moving insects that feed on plant sap and can weaken a plant significantly if left unchecked. Dab visible clusters directly with a cotton swab dipped in rubbing alcohol, then follow up with insecticidal soap across the whole plant weekly until they're gone.
Small dark flies hovering around the soil surface, especially after watering, are fungus gnats — a strong sign the soil is staying wetter than it should between waterings, since their larvae need consistently moist soil to develop. Letting the top inch or two of soil dry out fully between waterings breaks their breeding cycle, and yellow sticky traps placed near the soil catch the adults in the meantime.
Small, round, immobile bumps on stems and the undersides of leaves — often brown or tan and easy to mistake for a natural part of the plant at first — are scale insects, which feed on sap from underneath a protective waxy shell. Scrape them off gently with a fingernail or soft brush, then treat with insecticidal soap or neem oil, since the waxy coating makes them more resistant to spray-only treatments.
Small, soft-bodied insects — green, black, or brown — clustering on new growth and flower buds are aphids, which excrete a sticky residue ('honeydew') that can attract ants or develop sooty mold. A strong spray of water knocks most of them off, followed by insecticidal soap on the remainder and repeat treatment after a week to catch any that were missed.
Quarantine any new plant away from the rest of your collection for 1-2 weeks before placing it nearby — most infestations start with a single new arrival. Inspect leaves (including undersides) every few weeks as a habit, since catching a pest early makes it dramatically easier to treat, and keep a light neem oil routine going during the growing season as prevention rather than waiting for a visible problem.
Not sure exactly what you're looking at? LeafRx's free diagnose tool can take a photo and help identify the specific pest or disease, with step-by-step treatment guidance.