Spider mites: how to spot them and get rid of them
Pale speckling on the leaves and fine webbing underneath. How to tell spider mites from soil mites, what actually kills them and what neem oil misses.
The pale speckling across a leaf like that is spider mites, tiny relatives of spiders that live on the underside and feed on sap. They come off, though never in one pass. Everything here is written for houseplants, because indoors these mites get conditions the outdoors never gives them.
Early signs of spider mites, before you see the webbing
The first sign of spider mites is on the leaf rather than on the mite, and it shows weeks before you can make one out. Thin leaves give it away first, so a Calathea or a fern is where you start looking if several plants stand together.
- Pale stippling on the upper surface. They pierce cells one at a time from underneath, so the marks appear on the side facing you. Tiny dots, lighter than the leaf, scattered with no pattern.
- Colour draining out of the leaf. It looks dull first, then takes on a bronzed or dusty cast across the whole blade. By then the colony is large.
- Fine webbing between the veins. This arrives late, once they have been there a while. Webbing does not mean the plant is finished.
- Edges drying with the middle still green. The leaf dries inward from the rim and eventually drops.
- New growth coming out wrong. Young leaves open small or misshapen, because the plant is losing sap while it builds them.
What spider mites look like, and why some are white and some red
Spider mites are mites rather than insects, which is the distinction that decides what works on them, because a product labelled for insects may not reach a mite at all. They are small enough that almost everyone finds the damage first. The Missouri Botanical Garden puts an adult at about a fiftieth of an inch, which is a moving speck and nothing more.
Colour is where most people get stuck, and it identifies almost nothing. The species commonly found on houseplants runs pale green through yellow to red depending on the stage and the time of year, and other species are red throughout. Pale ones, red ones and the ones people describe as white can all be the same problem, so identify by where they sit and what the leaf looks like instead.
One white thing on a leaf is not this pest at all. A lump that lifts off whole when you press it with a nail is a mealybug, a different animal and a different job.
What you will not see without a lens are the eggs. They sit on the underside among the webbing, and nothing you spray gets inside one. Every method on this page therefore ends in repetition, and that is why, said once here rather than in every section that rests on it.
Soil mites vs spider mites: which one is in your pot
What runs across the surface of the compost is usually not what is eating your leaves. Soil mites live in the top layer of damp potting mix and feed on decaying organic matter, so finding them tells you the mix is wet and rich, not that your plant is under attack.
There is one honest overlap worth knowing. Spider mites shelter in crevices around a rim and in debris on the compost surface, so checking the pot as well as the plant is genuinely good advice, just for a different reason from the one most people give. You are looking for a place where they hide between treatments, which is a different thing from a population living in the mix.
How to get rid of spider mites in five steps
What decides the outcome is the order rather than the product you buy. Each step is worth less if you skip the one before it.
Does neem oil kill spider mites, and what it misses
Neem oil kills the spider mites it lands on and nothing else, and everything below follows from that limit. It works by contact and by putting them off feeding, so a thorough application on the undersides does real work and a quick mist over the top of the plant does almost none.
The second thing to know is that you are probably buying one of two different products. Cold-pressed neem oil and a refined azadirachtin concentrate are sold under the same name at strengths that are not comparable, and the dilution on one label will be wrong for the other. Read which one is in the bottle before you mix anything.
What it misses are the eggs, as does every other contact treatment. That makes it a reasonable answer for a few leaves on one plant, where you can turn every leaf over and get at it properly, and a poor answer for a large plant you cannot physically cover.
A product claiming to kill them instantly is a separate matter, and the questions at the foot of this page deal with it.
Spider mites treatment: what each type actually reaches
The best spider mites treatment is whichever one reaches the stage you are dealing with, and the label is where that is written. Work down the table by what you have in front of you rather than by the name on the bottle.
Two rows deserve a sentence more. Soaps and oils have to touch the mite to kill it, so a careful application on top of the leaf and a careless one underneath amount to not having treated at all. And broad-spectrum insecticides frequently cause mite outbreaks, because they remove the predators that were holding the population down without your ever knowing they were there.
Which substances are approved differs by country and by whether the plant is indoors or out, and the label settles it. The decision itself turns on scale. It is a few marked leaves on one plant against a shelf you have already cleared twice.
What eats spider mites, and when releasing predators is worth it
Plenty of things eat them, and outdoors that is most of the reason an infestation never gets going. Indoors none of them is present unless you bring them in yourself.
A release needs conditions the pest already likes, which is the awkward part of recommending one. Predatory mites want steady warmth and humidity, and a heated flat in winter gives them neither reliably. UC IPM puts the working ratio at roughly one predator for every ten spider mites, so a release is sized against the population rather than against the plant.
Where that leaves you is a question of scale. For one fern with a few marked leaves, this is an expensive answer to a small problem. For a wall of plants you have cleared twice and lost twice, it is the only approach that reaches the eggs, and the predatory species sold for glasshouse work are the ones to ask a supplier about.
Spider mites on plants indoors: what changes in a heated room
Spider mites on houseplants behave differently from the same animal on a garden plant. Indoors there is no rain, no wind and nothing that eats them, so a population that would be knocked back outside simply is not. A mite that meets rain, wind and predators outdoors meets none of the three in a living room.
Because nothing washes the plant, you have to. Outdoors a wet spell strips dust and mites off a leaf every few days, and nobody does that job in a living room. It is why a routine rinse of the undersides works better than something that simple has any right to.
Dry heated air is exactly the condition that favours their reproduction, which is why people find them in November rather than in June. Fine-leaved plants register it first, and a maidenhair fern sitting over a radiator has the fine leaves and the dry air at once.
A plant already short of light takes a long time to replace what it lost, so the damage stays visible for months after the mites have gone. If yours sits in a dark corner, it is worth knowing which low light houseplants genuinely cope before you blame the treatment for a plant that is not recovering.
Then there is a case apart, which is a plant hanging on a wall. The undersides face the wall, so the surface you never see is the one that has to be rinsed, and a Living Canvas or any other wall planter has that geometry problem. Take it down to treat it and let it drain before it goes back up.
A preserved or artificial wall cannot get this pest at all, because nothing on it is alive, and being alive is precisely what you give up in exchange for it never growing.
Where spider mites come from and how fast they build up
They come in on a plant, almost always a newly bought one, and warmth and dry air are what turn a handful into a population. After that they spread on foot, between leaves that touch, so a crowded shelf hands them every plant on it.
The speed is what catches people out. A plant you looked at a fortnight ago can go from clean to mottled between two waterings. An English ivy will carry a colony for a long while before it shows anything obvious, and that is how the ivy ends up reinfesting everything around it.
How to prevent spider mites coming back
Prevention here is a routine rather than a product, and all of it happens while you are watering anyway.
- Quarantine anything new. Keep a newly bought plant away from the rest for a few weeks before it joins the shelf. Almost every infestation walks in this way.
- Look at undersides while you water. Turn two or three leaves over on each plant. It costs seconds when the plant is already in your hand.
- Leave space between plants. Touching leaves are a bridge, and spacing costs nothing at all.
- Keep plants out of the driest spots. Fine-leaved plants and hot dry air are the combination that starts this, so move them or group them over a tray of damp clay pebbles.
- Check the whole plant, including the stems. Indoor succulents and trailing plants hide them along the stem behind the leaf, the side nobody turns over.
One hard call is worth stating plainly. A plant you have cleared and lost three times is a plant to give up on, because every round that plant survives leaves the plants around it exposed to another. If you want the growing conditions for any of the fifteen species this site documents, the plant care guide has them in one place.
Are spider mites harmful to humans or pets
Spider mites feed on plant sap, and none of the horticultural sources behind this page describes them biting or feeding on people or animals. They have no interest in anything that is not a leaf, and a mite that ends up on your hand while you are rinsing a plant is looking for a way off.
If something in the house is genuinely biting, it is a different animal and it is worth identifying properly rather than treating your plants harder. What can be said here is only what those sources describe, a pest of plants. Anything about a bite on a person belongs with someone who can look at it.
What we checked about spider mites
Everything on this page comes from five named horticultural sources and from the plants this site already grows and documents. What has not been measured is written down as not measured.
Conclusion - spider mites
Move the plant away from the others tonight and rinse every underside by hand, which is the step most people skip. From there the decision turns on how many plants are involved. One plant with a few marked leaves needs a repeated rinse and a soap made for plants. Once it is a shelf, you need a product whose label names mites, or a predator release.
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