Houseplant Pest Identification: What's on My Plant?

You can usually narrow down a houseplant pest from one clue: what you can actually see. Fine webbing and speckled leaves point to spider mites. White, cottony clusters in the leaf joints suggest mealybugs. Tan or brown bumps along stems and veins are usually scale. Tiny dark flies around damp soil are usually fungus gnats. Whatever you find, start the same way: move the plant away from the others, look closely, and wipe, rinse or prune off what you can before you consider any product.

Use the quick table to find your branch, then read that section to confirm it.

What you see	Likely cause	First step
Fine webbing; pale speckling or stippling on leaves	Spider mites	Tap a leaf over white paper; rinse foliage
White, cottony clusters in leaf joints and under leaves	Mealybugs	Isolate the plant; remove what you can by hand
Tan or brown bumps lined up along stems and veins	Scale	Flake them off with a fingernail
Sticky leaves, sticky surfaces below, black film	Honeydew from scale, mealybugs, aphids or whiteflies	Wipe the leaves, then find the insect above
Small dark flies around the pot	Fungus gnats	Let the soil surface dry; empty saucers; check drains
Pale or silvery streaks with dark specks	Thrips	Rinse both sides of leaves; trim damaged growth
Clusters of soft insects on new shoots and buds	Aphids	Knock them off with a strong spray of water
Tiny white "moths" that flutter off when you touch the plant	Whiteflies	Isolate; use yellow sticky cards to gauge numbers
Holes, spots or damage but no insects	Possibly not a pest	Review light, water and handling first

Start here: what do you see?

Fine webbing or speckled, stippled leaves: spider mites

Spider mites are arachnids, related to spiders and ticks, not insects, according to Iowa State University Extension. They are tiny: University of Illinois Extension puts them at about 1/50 inch. Their feeding empties leaf cells and leaves pale flecks, a pattern called stippling. They usually live on leaf undersides, so they often go unnoticed until the damage is obvious (University of Maryland Extension). The RHS describes the signs as fine webbing with straw-coloured speckling. Prominent webbing around leaves, buds and stems means a large population.

To confirm, hold a sheet of white paper under a leaf and tap the foliage sharply. Mites show up as tiny moving specks. A 10x magnifier helps. Indoors, mites can be a problem in any season, and the aroid family, which includes pothos and Monstera, is commonly affected (UMD). Rinse the foliage thoroughly in a shower or outdoors. Iowa State notes that raising humidity can slow mite population growth. For pothos-specific steps, see bugs on pothos.

White cottony clusters in leaf joints: mealybugs

Mealybugs are white, cottony insects that often cluster in leaf axils (the angle where a leaf meets the stem) and on leaf undersides (Iowa State). Their bodies are covered in powdery wax and taper towards the tail. They also turn up on stems, inside flowers and even on the outside of the pot (UMD). Feeding can cause yellowing leaves, stunting and dieback. Isolate the plant straight away so they don't spread.

Brown or tan bumps along stems and veins: scale

Scale insects look like small bumps or scales lined up along stems and leaf veins, usually on the underside (Iowa State). Adult females don't move and are covered in a waxy shell (Illinois Extension). Brown soft scale, a common houseplant pest, is oval and light tan, yellow-green or yellow-brown with darker mottling. Armoured scales such as fern scale are flatter and shaped like a pear or an oyster shell (UMD). The RHS describes them as light brown, limpet-like insects on stems and leaf undersides.

The main sign of soft scale is honeydew on the leaves or on surfaces under the plant. Damage includes yellowing, early leaf drop, stunted growth and dieback. Scale should flake off with pressure from a fingernail, and Illinois Extension suggests a piece of plastic such as an old card. Colorado State University Extension notes that scale usually comes into the home on infested plants. Plant-specific guides: scale on pothos and scale on Monstera.

Sticky leaves or a black sooty film: look for honeydew makers

Stickiness is a clue, not a pest in itself. Many sap-feeding pests excrete honeydew, a sugary waste, and black sooty mould can grow on it (Illinois Extension). Scale, mealybugs, aphids and whiteflies all produce it. Honeydew is a bigger problem indoors because no rain washes it off (UMD). Look on the leaves and stems directly above the sticky patch for the insect responsible. Wiping leaves with a moist sponge or paper towel removes both the insects and the sooty mould.

Tiny dark flies around the soil: fungus gnats

Fungus gnats are small, dark flies often seen around lamps, windows and pots with moist soil. Their larvae live in damp potting mix, especially mixes with lots of organic matter, and also in drains with moist debris (UMD). They are a nuisance rather than a threat: both Iowa State and UMD say they don't cause notable damage to indoor plants.

Because they need moist soil, fungus gnats are a good sign of overwatering. Let the soil surface dry out between waterings. Never leave a pot standing in a saucer or outer pot full of water. Check unused drains and condensation trays too (Iowa State). Yellow sticky cards catch adults but won't stop new ones hatching. For soggy-soil problems, see overwatered pothos and yellow mould in plant soil.

Silvery streaks with black specks: thrips

Thrips are small (2 mm or less), shaped like a grain of rice, and yellow, brownish or black (UMD). Their feeding leaves pale or silvery streaks. Their droppings show as small, dark, tar-like spots near the damage. Leaves that are still expanding while thrips feed can become stunted, crinkled or curled. Check young leaves, leaf margins, along the main vein and inside flower buds. African violets and their relatives are among the indoor plants often affected. See also thrips on Monstera.

Clusters on new growth: aphids

Aphids are small, soft-bodied, pear-shaped insects, often green, brown or reddish. They cluster on growing tips, leaf undersides, stems and flower buds (Iowa State, Illinois Extension). White shed skins often stick to the plant near a colony, and young leaves can end up stunted, crinkled or curled (UMD). A forceful spray of water dislodges most aphids, and you can trim off curled leaves with aphids still inside.

Tiny white "moths" that flutter off when touched: whiteflies

Adult whiteflies look like tiny white moths and flutter away when the plant is disturbed. The young are flat discs on leaf undersides. Heavy infestations cause stunted, distorted, discoloured leaves and sticky honeydew (UMD). Iowa State notes that whiteflies are highly mobile and hard to control. Yellow sticky traps are useful for gauging numbers, but they won't clear an infestation.

Damage but no insects: it may not be a pest

Not every damaged leaf has a bug behind it. UMD's indoor plant diagnosis table lists stresses unrelated to insects or disease. It gives water spots, sunburn, fungi and bacteria as possible causes of leaf spots. If a plant spent the summer outside, chewed leaves may come from caterpillars or beetles picked up there. Work through the cause before treating anything: holes in pothos leaves, brown spots on Monstera, black spots on Monstera, pothos problems and Monstera problems each start with a diagnosis.

How to inspect a plant properly

Turn the leaves over. Many pests hide on leaf undersides, so start there (Illinois Extension). Colorado State notes that spider mites are usually found on lower leaves.
Do the white-paper tap test. Tap foliage over white paper and watch for moving specks, which suggest spider mites (Iowa State, UMD).
Use magnification. A 10x lens may be needed to see spider mites, and thrips are hard to see well without one (UMD).
Check the stems, flowers and pot. Mealybugs can sit on stems, in flowers and on the outside of the container (UMD).
Use yellow sticky cards to monitor. Placed in or near the pot, they show whether fungus gnats or whiteflies are around and roughly how many. They are a scouting tool, not a cure (Iowa State, UMD).
Check often. Problems are easiest to handle while populations are small (Iowa State).

First moves for any pest: isolate, remove, rinse, prune

Isolate the plant so pests can't spread to your other houseplants (Iowa State, UMD).
Wipe the leaves with a moist sponge or paper towel. This removes insects, mites and sooty mould (Illinois Extension).
Rinse the foliage in a shower or with a strong spray of plain water, covering both sides of the leaves. Repeating this several times helps against aphids, spider mites and similar pests (Iowa State, Illinois Extension, UMD).
Scrape off scale with a fingernail or a piece of plastic.
Prune heavily infested leaves or branches, curled leaves hiding aphids, and leaves or flowers disfigured by thrips (Iowa State, UMD).
Fix the conditions that helped: let the soil surface dry and empty saucers for fungus gnats, and raise humidity for spider mites (Iowa State).
Re-check the plant and its neighbours over the following weeks, especially leaf undersides.

When a product is needed

If hands-on steps don't keep up, a pesticide may be the next step. Illinois Extension stresses three points. The product must be labelled for use on indoor plants. Contact products, such as insecticidal soaps, only work where they touch the pest, so coverage matters. Systemic products move through the plant, and many are toxic to bees, so use caution with plants that flower, especially if they will spend time outdoors. Colorado State adds that you should check the label lists your plant, to avoid damaging it. Choose a product labelled for both the pest and the plant, and follow the label exactly. For advice on your situation, contact your local cooperative extension service.

When discarding the plant is the better call

It can feel wasteful, but extension specialists are consistent. Iowa State says destroying a heavily infested plant before the pests reach nearby plants is the better choice, particularly with mobile whiteflies. UMD gives the same advice for heavy infestations of mealybugs, scale, mites, thrips and whiteflies. Illinois Extension says replacing a severely infested plant helps stop pests spreading to the rest of your collection.

Prevent the next infestation

Inspect before you buy. Both the RHS and Colorado State advise checking plants for pests before purchase. Scale in particular usually arrives on infested plants.
Quarantine new arrivals. Keep new plants apart from the rest, and keep checking them.
Check plants coming back indoors. Many houseplant pests are picked up while plants are outdoors for the summer (Purdue Extension). Before bringing them in, check the foliage and the potting mix. Flush pots with water to drive out soil insects and hose pests off the leaves. Then keep the plants apart for 3 to 4 weeks before moving them near others (Illinois Extension).
Don't overwater. Wet potting mix and standing water invite fungus gnats.
Make inspection routine. A quick look under the leaves whenever you water catches problems early.

For plant-by-plant care notes, browse our plant profiles.

Frequently asked questions

What are the tiny white bugs on my houseplant?

Usually mealybugs or whiteflies. Mealybugs are white and cottony, often clustered in leaf joints and under leaves. Whiteflies look like tiny white moths and flutter off when you touch the plant. White flecks near a cluster of aphids may be the aphids' shed skins.

Why are my houseplant's leaves sticky?

Sticky leaves usually mean honeydew, the sugary waste of sap-feeding pests such as scale, mealybugs, aphids and whiteflies. Black sooty mould can grow on it. Check the leaves and stems above the sticky area for the insect, and wipe the leaves with a damp cloth.

What are the small black flies in my plant's soil?

Most likely fungus gnats. Their larvae live in moist potting mix. University extension services say they don't cause notable damage to indoor plants, but their presence suggests the mix is staying too wet. Let the soil surface dry between waterings, empty saucers, and check nearby drains.

Do yellow sticky traps get rid of houseplant pests?

No. Yellow sticky cards catch flying adults such as fungus gnats and whiteflies, which makes them useful for monitoring. They don't stop new insects hatching or clear an infestation.

Can I just wash bugs off my plant?

Often, yes, as a first step. Rinsing in the shower or with a strong spray of plain water knocks off aphids and spider mites, and wiping leaves removes insects and sooty mould. Repeat it several times and isolate the plant meanwhile. Heavy infestations may need a labelled product or removal of the plant.

Should I throw out a plant with pests?

Only if it's heavily infested. Extension services advise discarding badly infested plants before pests spread, especially with whiteflies, mealybugs, scale, mites and thrips. Light infestations can often be handled by isolating, wiping, rinsing and pruning.

What's on My Plant? How to Identify Houseplant Pests