Fine webbing between the leaves and a dusty, speckled look to the foliage — that is two-spotted spider mite, and Phytoseiulus persimilis is the fastest thing we sell for it. Bright orange and just large enough to see, each one eats about ten adult spider mites a day, or twenty eggs and larvae. It walks straight into the webbing that stops other predators and works the colony from the inside.
It is also about as simple as pest control gets. Nothing to mix, nothing to spray, no residue on the leaves and no re-entry interval — you tip them onto the plant and leave them to it. They hunt the undersides and the crevices where a spray never lands, they find the colony without your help, and spider mites cannot develop resistance to being eaten. Safe around people, pets and anything you plan to eat.
Two things decide whether it works. It wants humidity — 60% or higher, sustained — and it wants spider mites to eat, because that is the only thing on its menu. In a dry room Neoseiulus californicus is slower but holds on at 40%, and on a plant with nothing to hunt persimilis will not linger.
Best for: An active two-spotted spider mite outbreak with visible webbing or stippling, in humid conditions.
How many: Sizes go by plant count. Deal with heavy webbing first — take the bulk of it off with a jet of water so the mites can reach the leaf surface where the eggs are.
Arrives as: A bottle of loose mites through a carrier. Deploy the day it arrives; there is no holding option.
Speed: One release is often enough at light to moderate pressure, with a second 7–10 days later for a heavy outbreak. Once fresh leaves come in clean, the population is broken.
Safe around: People, pets, plants and food crops.
Not for: Broad, cyclamen, russet or rust mites, or European red and spruce spider mite — those are different predators' jobs. And not a clean plant.
Field Notes
Phytoseiulus persimilis
The beneficial
Species
Phytoseiulus persimilis
Type
Predatory mite — an obligate specialist
Size
Slightly larger than a spider mite. Tear-drop shaped, bright orange to red, and very fast-moving
How it works
Moves rapidly across the leaves and navigates through spider mite webbing, which traps other predators — it walks into a web and works the colony from inside it
What it eats
Hunts
Two-spotted spider mite (Tetranychus urticae), all stages — eggs, nymphs and adults
Best against
Visible spider mite damage, webbing, or high pest counts — an active outbreak, not a clean plant
Won't touch
Anything that is not a spider mite. No pollen, no fungus, no debris, no alternative menu. It cannot survive without spider mites, so do not release it preventatively where there are no pests
What arrives
Format
Bottle of loose mites through a carrier that provides humidity and cushioning. Under good light you can sometimes see them moving against the pale grains. Everything in the bottle goes onto the plant
Where it works
Optimal temp
Active between 59°F and 86°F, ideally below 85°F — in extreme heat spider mites reproduce faster than Persimilis does
Humidity
60% relative humidity or higher, sustained. In drier air their eggs shrivel and fail to hatch. If your humidity fluctuates, use Californicus instead
Establishes
No. Once the spider mite population crashes the Persimilis population crashes shortly after, because it has run out of food — that is the design, not a defect. It will not linger on a clean plant, and if the mites return later you re-apply
Running it
Deploy
The day they arrive. There is no holding option for loose mites — releasing them in imperfect conditions beats holding them in perfect ones. Mist the plants lightly first, then rotate the bottle gently so the mites redistribute through the carrier
Placement
Onto infested foliage — hot spots first, clean plants never. Target the upper canopy and fresh growth where spider mites congregate, undersides included, because carrier dusted only on top surfaces mostly lands on the floor. Applying directly onto the webbing is encouraged
Replace
A single release is often enough for light to moderate pressure. For a heavier outbreak, a follow-up 7–10 days later, and a third only if live mites are still showing on new growth
Compatible with
Neoseiulus californicus — Persimilis onto the hot spots, Californicus across the rest of the crop as a patrol force that cleans up stragglers
Keep separate from
Sulfur is 21 days — wait 21 days after any sulfur application before releasing. And never with a sulfur burner running in the same space, at any dilution. Heavy webbing too: take the bulk of it off with a strong stream of water or a vacuum before release, so the mites can reach the leaf surface where the eggs are
Chemical interval
Horticultural oil is done once it is dry. Neem is contact only. Insecticidal soap needs a day. Sulfur is 21 days — wait 21 days after any sulfur application before releasing. And never with a sulfur burner running in the same space, at any dilution. Rinse oils and soaps off thoroughly with water first — residues kill predatory mites as easily as they kill the pests
Safe around
Plants, humans and pets
