Phytoseiulus persimilis — Predatory Mites for Spider Mite Control
How to Say It: fy-toh-SY-yoo-lus per-SIM-ih-lis
Natural spider mite control that hunts inside the webbing.
Fine webbing, stippled yellow leaves, and tiny mites crawling along the undersides are signs that two-spotted spider mites have moved in. When that happens, you need a predator that goes straight into the webbing after them. Release it right where the damage is worst. P. persimilis is built for fast, focused cleanup of active infestations, not for long-term prevention.
A Specialist Predatory Mite
P. persimilis is a Type I predator, which means it feeds only on webbing spider mites. Generalists like Amblyseius andersoni or Neoseiulus californicus can get by on pollen or other prey, but P. persimilis puts all its effort into one target. That focus makes it extremely effective, but it comes with two conditions:
- It needs prey. Once the spider mites are gone, the P. persimilis population dies off as well.
- It needs humidity. Its eggs need about 70% relative humidity inside the plant canopy to hatch, so it struggles in dry rooms and arid climates.
Pest Targets
Tetranychus species of webbing spider mites including:
- Two-spotted spider mite
- Carmine spider mite
- Pacific spider mite
- Strawberry spider mite
How It Controls Spider Mites
P. persimilis has a pear-shaped body that ranges from bright orange to red, and long front legs. Its small size lets it slip through dense spider mite webbing that keeps other predators out. Females lay oval, translucent eggs on leaf undersides near spider mite colonies. Adults and nymphs eat spider mites at every life stage, from eggs to adults.
When to Use It
Release P. persimilis as soon as you see webbing and spider mite activity concentrated on particular plants or sections. It works in gardens, greenhouses, and on houseplants, and it does best wherever humidity stays high. In dry conditions, N. californicus is usually the better choice.
Choosing Bottles or Sachets
Bottled Mites: Rapid Response
- A concentrated dose of adults ready to start hunting as soon as they’re released
- The fastest way to bring down an infestation that has already taken hold
- Suitable for houseplants, garden beds, greenhouses and larger growing areas
- Can be repeated weekly or every other week until the mites are under control
Sachets: Steady, Ongoing Release
- Each sachet holds mixed life stages and mites leave the sachet gradually over 2–4 weeks
- Keeps fresh predators moving onto infested plants without repeated handling
- Works best alongside or after a bottled release on active infestations, not as a stand-alone preventive
Application Rates
These are general starting points. Adjust actual application based on pest pressure, plant type, and infestation severity, and keep checking pest and predator levels to see how the program is working.
Bottled Mite Release: Fast coverage
- Light infestation: 1–2 mites per sq. ft. Every 2 weeks
- Heavy infestation: 2–4 mites per sq. ft. Weekly or every 2 weeks
Sachet Release: Slow release
- Plants touching: hang 1 sachet per 3–6 sq. ft.
- Plants not touching: hang 1 sachet per plant.
- Replace every 2–4 weeks.
Temperature and Humidity
Temperature: 68°F – 90°F
Humidity: 60–95%, with about 70% in the plant canopy needed for eggs to hatch
Application Instructions
Bottled
- Release in the early morning, in the evening, or under low light.
- Lightly mist the leaves to raise humidity around the plants.
- Gently rotate the bottle to mix the mites through the carrier.
- Sprinkle the contents onto the leaves with the most webbing and damage, or use hanging boxes to keep the mites in the target zones.
- Leave the open bottle near the plants for up to 72 hours so any remaining mites can find their way out.
- Repeat every 1–2 weeks until spider mite activity drops.
Sachets
- Pick the plants or sections with the heaviest spider mite activity.
- Hang each sachet in the canopy, out of direct sunlight.
- Keep sachets from drying out, but avoid spots that stay wet, which can encourage mold.
- Replace every 2–4 weeks while spider mites are present.
Pairing for Heavy Infestations
- N. californicus: a generalist that tolerates lower humidity and can survive without prey. Use it alongside P. persimilis to cover drier areas and to keep protection in place after hot spots are cleared.
- Stethorus punctillum (Spider Mite Destroyer): a small beetle that eats large numbers of spider mites. It’s useful on heavy infestations and taller plants.
- Feltiella acarisuga: a predatory midge whose adults fly to spider mite colonies and lay eggs there, and whose larvae then feed on the mites. It reaches spots that crawling predators miss.
Safe, Sustainable Pest Management
- 100% natural, with no chemical residue
- Safe around people and pets
- Safe for edible crops
- Fits into existing IPM programs
- No protective equipment needed
Storage
Release P. persimilis as soon as it arrives for the best results. If you have to wait, keep the unopened container at 45–55°F, with 70-90% humidity, out of direct sunlight, and for no more than 24 hours. Never refrigerate below that range or freeze.
FAQs
Can I use P. persimilis indoors in a dry room?
P. persimilis can be used indoors, but its eggs need about 70% humidity in the canopy to hatch. If you can’t raise humidity around the plants, N. californicus will usually establish more reliably.
Should I choose P. persimilis or N. californicus?
Choose P. persimilis for a fast, aggressive cleanup of webbed hot spots in humid conditions. Choose N. californicus for drier conditions or longer-lasting protection, since it can survive when spider mites are scarce. Many growers use both.
What happens to P. persimilis after the spider mites are gone?
Because it feeds only on spider mites, its population dies off once its food runs out. If spider mites come back, release P. persimilis again.
Can I spray insecticidal soap or neem oil with P. persimilis?
Even natural sprays can harm predatory mites. If you need to spray, do it before releasing P. persimilis and wait until the residue has dried and worn off.