Common Houseplant Pests: Identification and Treatment

Houseplant pests are usually small enough to be invisible until an infestation is well established. By the time you notice yellowing leaves, sticky residue on surfaces, fine webbing, or tiny insects on the foliage, a population has been building for weeks. Early identification and prompt treatment prevent a minor pest issue from spreading across a collection. This guide covers the six most common houseplant pests: how to identify each one and the first treatment steps.

Spider Mites

What they look like: Spider mites are tiny arachnids, less than a millimeter long, that live on the undersides of leaves. They are often not visible to the naked eye until populations are large, but their damage is distinctive: fine stippling, tiny pale dots, on the upper leaf surface where the mites have pierced individual cells. As infestations grow, fine webbing appears between leaves and on stem junctions.

Plants commonly affected: Spider mites prefer warm, dry conditions and thrive on aroids, calatheas, and hibiscus. They are most common in winter when indoor heating reduces humidity.

Treatment: Isolate the affected plant immediately. Wash the plant thoroughly under a room-temperature shower or spray the foliage with water to dislodge mites and webbing. Apply neem oil solution or insecticidal soap to all leaf surfaces, particularly the undersides, every three to four days for two weeks. Raising humidity around the plant significantly reduces future mite pressure. For a comprehensive treatment plan including systemic options for heavy infestations, the spider mite control guide in the pest control section covers the full sequence.

Fungus Gnats

What they look like: Fungus gnats are small, dark flies about two to three millimeters long that hover around plant pots and fly up when the soil is disturbed. The adults are annoying but do not damage plants directly. The larvae, which live in the top few centimeters of moist potting mix, feed on organic matter and the fine root hairs of plants. Heavy larval infestations weaken plants and can stunt growth in seedlings.

Plants commonly affected: Any plant in consistently moist potting mix, particularly those in rich, peat-heavy substrates.

Treatment: Allow the potting mix to dry more thoroughly between waterings: fungus gnat larvae cannot survive in dry conditions. Yellow sticky traps placed at soil level capture adults and reduce the breeding population. Hydrogen peroxide soil drench (one part 3 percent hydrogen peroxide to four parts water) kills larvae on contact without harming the plant. Beneficial nematodes (Steinernema feltiae) applied to the soil are an effective biological control. For the full treatment plan including sticky trap placement and nematode application, the fungus gnat control guide covers the process.

Mealybugs

What they look like: Mealybugs are soft-bodied insects covered in white, cottony or waxy filaments that give them a powdery appearance. They congregate in leaf axils, at stem junctions, along stems, and on the undersides of leaves. A mealybug infestation looks like small patches or clusters of white fluff or cotton. They excrete honeydew, a sticky substance that coats leaves and encourages sooty mold growth.

Plants commonly affected: Succulents, hoyas, cacti, and tropical foliage plants are all susceptible.

Treatment: Isolate immediately. Remove visible mealybugs manually using a cotton swab dipped in rubbing alcohol, which dissolves their waxy coating and kills on contact. Apply neem oil solution or insecticidal soap to all plant surfaces, including soil surface where eggs may be present. Repeat every five to seven days for three weeks to break the life cycle. Check the plant weekly for several months after apparent clearance, as mealybugs hide in leaf axils and can re-emerge from overlooked eggs.

Scale Insects

What they look like: Scale insects appear as small, flat or domed oval bumps attached firmly to stems and the undersides of leaves. Unlike mealybugs, they do not have a visible waxy filament coating; instead they produce a hard or soft protective shell over themselves. Soft scale is waxy and slightly raised; armored scale is harder and flatter. Both are easy to mistake for part of the plant stem until you try to remove them with a fingernail, at which point they scrape off revealing the insect underneath. Like mealybugs, they excrete honeydew that causes sticky foliage and sooty mold.

Plants commonly affected: Ficus, bay laurel, citrus, and many aroids.

Treatment: Remove scale physically using a soft toothbrush or cotton swab dipped in rubbing alcohol. Apply horticultural oil or neem oil solution to all stem and leaf surfaces, which smothers scale under their shells. Repeat every seven to ten days for three to four weeks. Armored scale is more resistant to treatment than soft scale because the hard shell protects against contact insecticides.

Thrips

What they look like: Thrips are very small, slender insects one to two millimeters long, typically pale yellow or dark brown. They feed on leaf cells by rasping the surface and sucking out the contents, leaving distinctive silver or bronze streaking, scarring, and stippling on the leaf surface. Black specks of excrement are often visible alongside the feeding damage. Thrips also damage flowers and spread quickly to neighboring plants.

Plants commonly affected: Calatheas, monstera, peace lily, and many flowering plants.

Treatment: Isolate the plant. Shower the plant thoroughly to remove adults and nymphs. Apply spinosad-based insecticide, neem oil, or insecticidal soap to all leaf surfaces every four to five days for three weeks. Thrips have multiple life stages including pupation in the soil: a soil drench with neem or spinosad addresses soil-dwelling pupae. Blue sticky traps catch adult thrips.

Aphids

What they look like: Aphids are soft-bodied, pear-shaped insects two to three millimeters long, typically green, yellow, black, or brown depending on species, that cluster on new growth, flower buds, and the undersides of leaves. They feed by sucking plant sap and reproduce rapidly: a single aphid can produce dozens of offspring in a week without mating. Heavy infestations cause distorted, stunted new growth and copious honeydew.

Plants commonly affected: Roses, herbs, flowering houseplants, and any plant producing soft, succulent new growth.

Treatment: Remove by hand or with a strong jet of water. Apply insecticidal soap or neem oil to affected areas every three to four days. Aphids are relatively easy to control compared to spider mites or scale: they do not have protective coatings and are vulnerable to most contact treatments. Ensure all undersides of leaves and growing tips are treated, as aphids hide in leaf folds and at stem bases.

General Pest Management Principles

Inspect new plants thoroughly before bringing them home, quarantine them for two to four weeks away from your existing collection, and check under leaves and in leaf axils before they join the main group. This single practice prevents the majority of houseplant pest introductions. For plants already in your collection, a weekly inspection of the undersides of leaves on susceptible species catches infestations at a manageable stage.