Houseplant pests are small, persistent, and easy to miss until they have spread. A spider mite is barely visible; a mealybug hides in a leaf joint; a fungus gnat looks like a harmless tiny fly. By the time the damage is obvious — yellowed leaves, sticky honeydew, a plant that has stopped growing — the pest has usually been there for weeks and may have spread to the plants next to it. The defence is inspection: a weekly look at the undersides of the leaves, with a magnifying glass if you have one, will catch almost every pest while it is still a ten-minute job.
This guide covers the pests that actually attack houseplants, how to identify each one, and the control that works indoors, where you cannot use the sprays you might use in a garden. If a pest does not match anything here, the pest identifier helper can help you compare, and your local extension service can confirm an identification from a photo or a sample.
Spider mites: the fine webbing on calathea and monstera
Spider mites are tiny, barely visible red or brown mites that live on the undersides of leaves and suck the sap, leaving fine stippling — tiny pale dots — and, in a bad infestation, fine webbing between the leaves and the stem. They love warm, dry air, which is why they are worst in winter in a heated home, and they attack the calathea medallion, the monstera deliciosa, the fiddle-leaf fig, and the bird of paradise most often. Control starts with humidity: mites hate damp air, so group plants together and raise the humidity around them. Wash the plant in the shower or with a strong jet of water, paying attention to the undersides of the leaves, and repeat every few days. Remove the worst-affected leaves. A spray of water with a drop of washing-up liquid can help, but test it on one leaf first, since it can damage sensitive plants. Isolate the affected plant at once — spider mites spread quickly to neighbouring plants, and a single infested plant can infect a whole collection in a month.
Mealybugs: the white cotton on pothos and philodendron
Mealybugs look like small pieces of white cotton wool in the leaf joints and on the undersides of the leaves, and they suck the sap, weakening the plant and producing sticky honeydew. They attack the golden pothos, the philodendron Brasil, the monstera deliciosa, and the rubber plant, and they hide in the places that are hardest to reach. Control is hands-on: dab each mealybug with a cotton bud dipped in rubbing alcohol, which kills it on contact, and repeat weekly until no new ones appear — it usually takes several weeks, because the eggs hatch over time. Wash the plant in the shower to remove honeydew. Isolate the plant, since mealybugs spread to neighbouring plants, and check the plants next to it. Do not use a broad-spectrum insecticide indoors, and do not rely on a single treatment: mealybugs are a pest that needs persistence, and a plant that is declared clear too early will be infested again within a fortnight.
Fungus gnats: the tiny flies from wet soil
Fungus gnats are small black flies that hover around the soil surface, and their larvae live in the top few centimetres of the mix, eating organic matter and fine roots. The adults are harmless but irritating; the larvae can damage seedlings and young plants. They are a sign that the mix is staying too wet, which is the real problem to fix: let the top few centimetres of mix dry out between waterings, and the gnats will decline on their own. Yellow sticky traps catch the adults and tell you how bad the infestation is. A layer of fine grit or sand on the surface of the mix stops the adults from laying eggs. Watering with a biological control containing Bacillus thuringiensis israelensis (Bti) kills the larvae without harming the plant. Do not overwater to compensate — the gnats are a symptom of wet soil, and the cure is drier soil, not more water. Our houseplants watering guide explains the watering that prevents them.
Scale and thrips: the armoured and the invisible
Scale insects look like small brown or grey bumps on the stems and the undersides of the leaves, and they suck the sap while protected by their hard shell. They attack the rubber plant, the fiddle-leaf fig, and the bird of paradise. Scrape them off with a fingernail or an old toothbrush, dab the spot with rubbing alcohol, and repeat weekly — sprays cannot penetrate the shell, so physical removal is the only reliable control. Thrips are tiny, thin insects that rasp at the leaves and leave silvery streaks and distorted growth, and they are hard to see without a magnifying glass. They attack the monstera deliciosa and the philodendron Brasil. Blue or yellow sticky traps catch the flying adults, and washing the plant regularly helps. Both pests are worst on a plant that is stressed — by too little light, too much water, or a pot that is too small — so fix the conditions as well as removing the pest.
Quarantine and prevention: the habits that matter
Prevention is worth more than any treatment. Quarantine every new plant for two weeks, away from your other plants, and inspect it before mixing it in — most infestations arrive on a new plant from a shop. Inspect your plants weekly, looking at the undersides of the leaves and in the leaf joints, where pests hide. Do not overwater, since wet soil invites fungus gnats and root rot. Do not overcrowd your plants, since pests spread fastest where leaves touch. Clean the leaves regularly with a damp cloth, which removes dust and some pests at the same time. And when a plant is badly infested and you cannot control it, consider throwing it away rather than risking the rest of your collection — a single cheap pothos is not worth losing a monstera deliciosa and a fiddle-leaf fig to spider mites. If you are unsure about a diagnosis, a product, or a local rule, check your local extension service — its advice is tailored to your soil, climate, and the pests and diseases active in your area.
Frequently asked questions
What are the tiny white bugs on my pothos?
Usually mealybugs, which look like small pieces of white cotton wool in the leaf joints. Dab each one with a cotton bud dipped in rubbing alcohol, and repeat weekly.
What are the tiny black flies around my houseplants?
Fungus gnats. Their larvae live in wet soil. Let the top few centimetres of mix dry out between waterings, use yellow sticky traps, and add a layer of grit on the surface.
How do I get rid of spider mites on my monstera?
Raise the humidity, wash the plant in the shower, paying attention to the undersides of the leaves, and repeat every few days. Isolate the plant at once.
What are the brown bumps on my rubber plant?
Scale insects. Scrape them off with a fingernail or a toothbrush and dab the spot with rubbing alcohol. Sprays cannot penetrate their shell.
Should I quarantine a new houseplant?
Yes, for two weeks, away from your other plants. Most infestations arrive on a new plant from a shop, and quarantine catches them before they spread.