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Biological control · Spider Mites
Tetranychus urticae (two-spotted spider mite) and related species
Spider mites are tiny mites that feed on the undersides of leaves, leaving fine pale speckling and, as the colony grows, webbing. They breed fast and shrug off sprays, which is why they keep coming back. Predatory mites eat every stage: persimilis goes into the webbing and clears active colonies, californicus handles warm, dry rooms and stays on the plant, and andersoni copes with swinging temperatures. Judge it by the new growth: when new leaves come in clean, it's working.
Illustration · not to scale1Confirm it
Fine pale speckling and webbing on the undersides of leaves mean spider mites. Your phone zoom shows them moving.
Getting the pest wrong is the most common reason treatment fails. Check the signs, or answer a few quick questions.
Fine pale dots, like the surface was sanded, often along the veins
Fine, dusty webs on the undersides, in leaf joints and at the tips
Speckling runs together until the leaf looks dull, bronze or yellow
Heavily fed leaves dry out and fall, often starting in the warmest spots
Quick check
Still not sure? Work backwards from the damage or send us a photo.
2Pick a plan
Pick by what you see: speckling only, webbing in an ordinary room, webbing in a humid room, or more than one pest.
Show me the plan for , across plants.
If you see
Pale dots on the leaves and tiny moving specks underneath
Neoseiulus californicus eats spider mites and handles warm, dry rooms. It lives on pollen when spider mites are scarce, so it stays on the plant after the first wave. Release on the speckled plants and their neighbors, and repeat every 2–4 weeks.
If you see
An established colony, in an ordinary or dry room
Persimilis and californicus together. Persimilis walks into the webbing and eats every stage; californicus copes with drier air and cleans up the stragglers. Every 2–4 weeks; more than one round is normal.
If you see
About 60% humidity or more, or you can keep it there
Phytoseiulus persimilis is the spider mite specialist. It goes straight into webbing that stops other predators and eats eggs, nymphs and adults. Take heavy webbing off with a jet of water first. Release again every 2–4 weeks while new leaves still pick up speckling.
If you see
Thrips, broad mites, or you can't tell which mite
Four predatory mites in one bottle (andersoni, californicus, swirskii and cucumeris) for mixed or unclear pests. If you know it's only spider mites, persimilis or Rapid Response is the better match.
Other spider mite plans
Good to know: Cold nights and hot days? Amblyseius andersoni works from about 43°F to 100°F and takes other pest mites too, so it's the one for rooms whose temperature swings.
Prefer to build it yourself? Shop each predator. Just want to keep spider mites out? See prevention. Not sure what you're seeing? Take the quick check.
Or build it yourself
Every predator and parasite we ship for spider mites, with bundles first when we have them.
How it works
Persimilis clears active colonies inside the webbing, californicus holds warm, dry rooms, andersoni covers swinging temperatures.
A spider mite goes from egg to egg-laying adult in about ten days in a warm room, and every stage lives on the underside of the leaf. Eggs, young and adults sit side by side, which is why one spray rarely ends it and why the predators have to eat every stage.
Illustration · not to scale
Eats spider mites at every stage, inside the webbing
Active outbreaks with webbing, in humid rooms. Every 2–4 weeks while new leaves still pick up speckling
Eats spider mites, and pollen when they're scarce
Early infestations and warm, dry rooms. Stays on the plant. Every 2–4 weeks
Eats spider mites and other pest mites
Rooms that swing between cool and hot, or when you're not sure which mite. Every 2–4 weeks
Eats spider mites at every stage
Established webbing in an ordinary room. Every 2–4 weeks
| Predator | Works on | Eats | Best for | From |
|---|---|---|---|---|
| Phytoseiulus persimilis | Leaves | Spider mites at every stage, inside the webbing | Active outbreaks with webbing, in humid rooms. Every 2–4 weeks while new leaves still pick up speckling | $55 |
| Neoseiulus californicus | Leaves | Spider mites, and pollen when they're scarce | Early infestations and warm, dry rooms. Stays on the plant. Every 2–4 weeks | $75 |
| Amblyseius andersoni | Leaves | Spider mites and other pest mites | Rooms that swing between cool and hot, or when you're not sure which mite. Every 2–4 weeks | $57 |
| Spider Mite Rapid Response | Leaves | Spider mites at every stage | Established webbing in an ordinary room. Every 2–4 weeks | $100 |
3After it arrives
Wait out sprays, rinse off heavy webbing, persimilis onto the hot spots, and repeat at the product's interval.
Before you order
Zoom in with your phone camera on the underside of a speckled leaf. Tiny moving specks, often with fine webbing, mean spider mites
While it ships
Note the plants with webbing or the heaviest speckling. That's where the first predators go
Neem and horticultural oil once dry; insecticidal soap one day. Wait 21 days after sulfur
Release day
Take the bulk of thick webbing off with a strong stream of water so predators reach the leaf surface. Light webbing can stay
Tip small piles near the webbing on flat leaf tops or leaf joints, worst plants first
Tap them onto the leaves of infested plants and their neighbors. They stay on when spider mites are scarce
Persimilis eggs hatch best in humid air. Group plants or run a humidifier if you can
After release
Persimilis, Rapid Response, californicus and andersoni: every 2–4 weeks while spider mites are active
Keep going until new growth stays clean two weeks in a row
These are the ranges they like best, not hard limits. Short spells outside them won't hurt; only conditions that last for days slow them down.
The speckling you already have stays. Those leaves were fed on before the predators arrived
Webbing stops spreading, and new speckling slows
New leaves come in without speckling
New growth stays clean two weeks running. A few stragglers aren't a new infestation
Most failed treatments come down to spray residue, a room too dry for persimilis, or judging by the old leaves.
Sprayed just before release
Residue harms predatory mites. Wait until neem or oil is dry, a day after soap, and 21 days after sulfur
Persimilis in a dry room
It does best around 60% humidity or more. In a dry room, use californicus or Rapid Response
Judged by the old leaves
Speckled leaves stay marked. Watch the new growth instead
Only the worst plant
Spider mites reach the neighbors before they show. Check and treat the plants around it
Heavy webbing left on
Thick webbing keeps predators off the leaf surface where the eggs are. Rinse the bulk of it off first
One round on a heavy outbreak
Repeat at the product's interval until new growth stays clean
4Afterwards
Hang prevention sachets before spider mites show up.
Spider mites usually arrive on a new plant, or build up on their own when the air turns hot and dry. Prevention sachets keep them from starting: hang one every 3 to 5 feet of shelf, or one on a large plant, and it releases predatory mites over four to six weeks, so they're already there when the first spider mites land. Persimilis sachets for humid rooms, californicus for hot, dry ones, andersoni where temperatures swing. Sachets won't catch up with webbing you can already see; that needs a bottle.
Want them on a schedule? Any prevention sachet can be set up as a subscription on its page. See the prevention sachets.
Same warm, dry rooms. Ultimate Control covers both with californicus, cucumeris and swirskii
Thrips treatment →Ultimate Control Predatory Mite Mix, from $90 →
Twisted new growth alongside spider mite speckling. Andersoni takes both
Broad and cyclamen mites treatment →Amblyseius andersoni, from $57 →
More about biological control in the Biocontrol FAQ, or ask us.
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Field Notes
If something’s wrong when it arrives, email info@fgmnnursery.com within 72 hours of delivery for a replacement or store credit.
By continuing to checkout you agree to our Shipping Policy and Live Delivery Guarantee.
If something’s wrong when it arrives, email info@fgmnnursery.com within 72 hours of delivery for a replacement or store credit.
By placing your order you agree to our Shipping Policy and Live Delivery Guarantee.
