Our Top PERSIMILISforce™ for Spider Mite Control
PERSIMILISforce™ for Spider Mite Control
A specialist predator of two-spotted spider mites — Phytoseiulus persimilis.
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What it targets
PERSIMILISforce™ is the trade name for Phytoseiulus persimilis, the predatory mite most growers reach for when a hot spot of two-spotted spider mite (Tetranychus urticae) is already running. P. persimilis is a strict spider-mite specialist — it can’t feed on anything else — and Cornell’s NYSIPM ranks it as the predatory mite with the highest consumption rate of any phytoseiid working against Tetranychus.
Primary host is the two-spotted spider mite. Carmine red mite (T. cinnabarinus) and Pacific spider mite (T. pacificus) are within range too, but they require higher release rates than the standard schedule. On crops where the population is moving fast or webbing is already visible, persimilis is the curative pick. For longer-term, lower-prey-density jobs — or for crops that swing dry and warm — pair with or substitute Neoseiulus californicus, which can hold on with little to eat.
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How it works
Under a sufficiently warm, humid canopy the predator population outgrows the prey: female persimilis develop roughly twice as fast as Tetranychus, lay up to 60 eggs over their lifetime, and place them right inside the spider-mite colony — including inside the webbing that T. urticae spins. That web is a barrier to most generalist predators; for persimilis it’s a hunting ground. Adults and the nymphal stages both feed, working through eggs, larvae, and active mites without slowing.
Optimum performance runs at 70–85°F with relative humidity between 60–90% (vendor); Cornell’s practical window is a little cooler at 62–80°F with 50–70% RH. Below those floors, reproduction slows and dispersal climbs — persimilis is a strong walker, and if prey thin out it will leave the crop looking for more. That trait makes it a curative predator, not a preventive one: release after spider mites are detected, not before. Outdoors in cool climates, no overwintering — plan on fresh releases each season.
The predator-prey ratio that turns a hot spot
In greenhouse and ornamental trials, spider-mite populations start to drop when the pest:predator ratio reaches roughly 5–10:1. Practically, that translates to 1–3 predatory mites per square foot for preventive cover where mites are first detected, 5 per square foot for low-to-moderate infestation, and 10 or more per square foot once webbing is visible.
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Crops, environments, and climate
Crops it supports
Vegetable crops
Fruit crops
Strawberries
Ornamental crops
Tree & shrub nurseries
Hemp / Cannabis
Environments
Greenhouses
Indoor facilities
Fields & row crops
Gardens
04
Storage
Don’t hold predators longer than 8 hours. Store the container on its side at moderate humidity, 55–65°F, until release. Persimilis is shipped in active form; cold-store conditions only extend a short window before viability drops.
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Instructions of use
Bottles with carrier
Tumble the bottle gently before opening to redistribute the predators through the carrier. Open in the crop area — not in the storage room — and tap the contents onto the foliage of the most heavily infested plants. Concentrate the bulk of the release at the hot spots and reserve some for a sweep through milder pressure. Leave the bottle in the treatment area for 24 hours after release so any remaining predators can climb out and find the canopy.
Vials with nipple cap
Vials ship with a nipple cap for slow, controlled dosing. Cut the tip to the opening size you want — a small opening releases slower than a larger one. Persimilis’s instinct is to run straight up, so keep the vial vertical: the mites will walk out of the opening on their own while you dab them onto the foliage along the canopy. Move plant to plant in a steady rhythm; the predators handle the rest.
Setting up for success
A light foliar misting just before release raises the local humidity and slows the spider mites — it helps the predator and hampers the pest at the same time. Avoid releasing in the heat of the day. Where plant canopies touch, persimilis disperses on its own; smooth, non-waxy leaf surfaces and connected plant rows are ideal. Crops with dense leaf hairs (some tomato cultivars, for example) physically slow the predator down and limit performance.
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Monitoring & advisories
Monitor for
- Undamaged new growth and webbing-free leaves after release — the most reliable sign persimilis is working.
- Empty webbing left behind in interiorscapes and some greenhouses, or missing webbing outdoors where the crop had it.
- Fast, orange, long-legged mites running across the leaf underside — the predator itself, easy to see with a 10× hand lens.
- Stippling on the upper leaf surface — the chlorotic spots from T. urticae feeding — should slow within 7–14 days of a release at adequate rate.
- Spider-mite eggs on the leaf underside (white, spherical) thinning out as the predator eats through them.
Advisories
- Be sure of the pest species. Persimilis only feeds on certain Tetranychus spp.; other mites (broad mite, russet mite, false spider mite) need different predators.
- Soil mites are not spider mites — persimilis is a foliar predator and won’t address soil-dwelling fungus or thrips pupae populations.
- Spider mites don’t fly. They crawl and ride air currents and clothing; restrict movement through hot spots and quarantine new plants to slow spread.
- Cool climates and short day lengths slow reproduction. Persimilis can’t overwinter in temperate zones; plan repeat releases each season.
- Some pesticide residues are lethal. Avoid bifenthrin, fenpyroximate, and acequinocyl in the weeks before release; allow at least four weeks after a broad-spectrum insecticide.
- Releases on tomato tend to underperform — the cultivar’s leaf hairs slow the predator. Pair with another control where tomato is the host crop.
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Release rates — for conventional crops
| Classification | Rate | Interval |
|---|---|---|
| Low infestation preventive | 0.5 per sq. ft. | Regular releases as needed |
| Moderate infestation active | 5 per sq. ft. (Cornell NYSIPM) | Re-release if mites rebound |
| High infestation — webbing visible active | 2–10+ per sq. ft. | Repeat as needed |
| Strawberry, outbreak active | 200,000 per acre (Cornell NYSIPM) | At first outbreak / webbing |
| Target pest:predator ratio is roughly 5–10:1. Scout 7–14 days after release; if mite counts haven’t turned, repeat before the next generation builds. | ||
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Cannabis Alert
Conventional release rates are usually not sufficient for cannabis growers. We recommend you double the rate or contact us for personalized help.
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Life cycle
The Phytoseiulus persimilis life cycle runs egg → larva → protonymph → deutonymph → adult. Immature development averages around 8 days under warm conditions; the adult phase runs roughly 36 days. Because the predator develops about twice as fast as the spider mite, populations climb quickly once prey are present.
1
Egg
2
Larva
3
Nymph
4
Adult
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See it in action
Disclosures
Live-product policy. Beneficial Insectary works to guarantee the live delivery of fresh organisms. Replacements or credits are offered for compromised shipments when customers report issues or concerns within 24 hours — before any organisms suspected of viability issues are released. Don’t discard the product; you may be asked to return the shipment for analysis.
Establishment of biocontrol agents. Many variables — pesticide applications, watering practices, storage methods, and other cultural, physical, or mechanical controls — can shift biocontrol-agent and pest populations. Some beneficials need a steady pest presence to build their numbers; others require pollen or nectar as alternate food; others have specific photoperiod requirements. Long- or short-term establishment after release can’t be guaranteed, and refunds, discounts, or credits are not offered on products that have already been released.