Amblyseius andersoni
Heads up—this is just an estimate. We only ship when the bugs are happy and ready to travel (Mon–Thurs). If a colony needs a beat to peak, or we're propagating a fresh batch, your order might hold up to a week. Treatment bottles jump the line when you've got an active infestation.
Sizing guide
How our sizes work
Sizes are set by how many plants you are treating — not by how much material is in the container.
Every size on every product page names its own coverage right there in the dropdown, so you never have to come here to find a number. Medium — Up to 25 Plants (2,500 Mites) tells you the tier and the count in one line. This page is for the part the dropdown cannot tell you: how to pick between two of them.
These are rough middles. The ladder runs smallest to largest within each product, so a Medium of one species covers more ground than a Medium of another — a nematode drench and a beetle release are not the same job. The count on the size you are looking at is always the real answer.
Pest pressure moves you up the ladder
Plant count is only half the sum. The other half is how much pest is already there. A closed tent holding fifteen plants with thrips on every growing tip needs a larger release than a bright room holding forty plants with a few gnats — the population you are outnumbering is bigger, and the enclosed space lets it rebound faster.
Coverage figures assume a typical active infestation. Adjust from there:
Under heavy pressure, two releases beat one large one. Take the larger size and plan a second release 7–14 days later, which catches the eggs that had not yet hatched the first time.
A few things work differently
A few products read in square feet rather than plants, because that is how they are applied — the outdoor and area-scale releases. Those are Sc and Hb nematodes, and the aphid specialists Ervi, Matricariae, and Aphidoletes. Same ladder, different unit.
Sf nematodes and Triple Blend size by plants and pots, like everything else. They are soil drenches for potted plants, so count your pots rather than your floor.
Slow-release sachets have no size. They are sold by the sachet, and you place one per plant or one per few plants depending on pressure. Sachets are a prevention tool — they hold a population in place before a problem starts. If something is already established, a bottle is the correct answer.
Sizing up is cheaper than sizing twice. Predators need enough prey to establish and enough of themselves to find it. Underdosing is the most common reason a release underperforms, and it usually costs more in the end than the larger size would have. When you are between two sizes, take the larger one.
Still not sure? Tell us what you are growing and what you are seeing, and we will size it for you.
Amblyseius andersoni
At A Glance
Andersoni is throwing a temper tantrum
They're refusing to work, so we're not shipping them. We don't know when they'll be back in stock.
The honest bit: no single mite we sell does exactly what Andersoni did. Its trick was the temperature range — it kept working in a cool room where most predators slow down. Here's what covers the same pests, and where each one is better or worse than what you're used to.
In the meantime
Neoseiulus californicus — not nearly so finicky
Happy to work in just about any room you put them in, as long as there's a spider mite to be found.
Same core pests: two-spotted spider mites, broad mites and cyclamen mites.
Handles dry air better than any other predatory mite we carry — heated room in winter, air conditioning in summer, they don't mind either.
Like Andersoni, they stick around on pollen and alternative prey once the pests are gone, so they don't vanish the moment they win.
Where they differ: thrips aren't their thing. If thrips were part of why you bought Andersoni, pair them up or use the blend below.
Special Blend — more than one pest, or you're not sure what you've got
Californicus, swirskii and cucumeris in one bottle: spider mites, broad mites, cyclamen mites, thrips larvae and whitefly immatures. Not russet or rust mites — nothing we stock covers those while Andersoni is away, and we would rather say so.
The nearest thing to Andersoni's covers-a-bit-of-everything role, and what we'd reach for on a mixed problem.
Amblydromalus limonicus — for a cool, less humid room
Stays active in a cooler house, which is the part of Andersoni people miss most.
They're after thrips and whitefly rather than spider mites, so it's a substitute for the climate, not for the pest list.
Amblyseius swirskii — for a warm, humid room
Thrips larvae and whitefly eggs, at their best above 68°F with decent humidity. The opposite end of the range from limonicus.
Still not sure?
Reach out to our bug pros at fgmnnursery.com/order-support. Tell them what the plant looks like and what the room runs at, and they'll tell you which one to send. If you'd rather work it out yourself, the Mite Matchmaker will get you there too.
Existing orders and past deliveries are unaffected. Our live delivery guarantee still covers anything you've already received.
Target Pests
Environmental Needs
Selection Guide
How to Use
How They're Shipped
Deploy day, and the weeks after.
How to deploy your order, and how to read the results over the next few weeks.
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01
Open the box right away
Bring the package indoors as soon as it arrives. Don't leave it on a hot porch, in a cold mailbox, or in direct sun. If you can't deploy immediately, set the bottle somewhere room-temperature (60–75°F) and out of direct light — it'll keep for a day or two.
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02
Let the bottle rest 15 minutes
Mites huddle in transit for warmth. Set the bottle somewhere room-temperature for fifteen minutes before you open it. This lets them spread back through the carrier and warm up before deployment.
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03
You probably won't see them
Predatory mites are smaller than a grain of salt. Most people can't spot them with the naked eye, and phone cameras can't focus close enough to catch them. That's expected! What you can check: the carrier material should look dry and uniform, the bottle should be intact, and there shouldn't be visible mold. A warm box is normal — don't read anything into it.
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04
Deploy the same day
Apply in the evening or on a cloudy day to avoid UV exposure. For pests on the plant — spider mites, thrips, broad mites — sprinkle the carrier material directly onto leaves and stems where damage is visible. For soil-dwelling pests like fungus gnats, sprinkle onto the top inch of soil and lightly water afterward to help the mites settle into the medium. Either way, spread across plants instead of piling in one spot. See the product description for species-specific dosing.
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05
Watch your plants over 1–2 weeks
The real "are they working" check isn't visual. It's whether your pest population drops. Bottled treatments typically show measurable reduction in spider mites, thrips, or other targets within one to two weeks. If pest pressure isn't easing by then, that's when to bring in our bug pros.
Something not quite right?
Reach out to our entomologist by filing a report within 72 hours of delivery, with your order number and a photo. Candidly, without a photo the team can't approve a live beneficial claim.
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FAQ
What is your Live Delivery Guarantee?
We guarantee that your beneficial insects arrive healthy and ready to work. They're living things, so we pack for the season and ship expedited to give them the best trip we can.
If something looks wrong when the box opens, take a photo and file a report within 72 hours of delivery, with your order number. Photos matter: candidly, without them the team can't approve a live beneficial claim.
Can I use Andersoni outdoors?
Will they eat my plants?
Can I use them with other mites?
How long do they live?
Does Andersoni work on Aphids?
Is it safe for my pets?
Help! I'm overwhelmed
Yeah, it's a lot the first time you're using predatory mites. File a report and our bug pros will walk you through it!
I don’t see anything moving in my bottle or sachet. Does that mean they’re dead?
Not at all! In fact, go ahead and deploy them.
Predatory mites are microscopic (often less than 0.5mm) and naturally blend into their carrier medium (bran or vermiculite).
- For Bottles: The mites often huddle in the center of the bottle for insulation during transit.
- For Sachets: These are "slow-release" nurseries. The mites stay tucked deep inside the breeding media and emerge one by one over 2–4 weeks. Seeing an "empty-looking" sachet or bottle is not proof of a loss; it is simply how they are packaged for maximum survival.
I had spider mites. I added this and they got worse! All my hopes are gonna burn with my plants. This colony has got to go
Hi Bakedj, thank you for the feedback, and we're sorry the mites have been winning so far. Spider mites reproduce fast — there's a point where they can nearly double day over day. If your beneficials arrived right as that surge hit, and the dose was matched to the smaller population you had before it, they'd be behind from the start and stay behind, since predators don't breed as fast as the mites do. Plenty of other things can play a part too — a sudden temperature swing or leftover pesticide residue can knock beneficials back — but the one thing that's true is this isn't lost yet. If you'd like help diagnosing what happened and figuring out where to go next, we're glad to talk it through. Our customer service team is at info@fgmnnursery.com.
Amazing customer service
This was my first time buying bugs. I used their find a bug search which had me put it the type of infestation and the type of environment the crop is in. They pointed me to the bugs I needed and shipped out the following day. The bugs showed up in the morning next day deliver for the predatory mites. There was a mix up on the amount of mites they sent, sent out they missing containers the next day.
It’s been a few days and the predatory mites have laid a beat down on the two spotted spider mites and should save me from having to spray anything while I flower.
I will be returning every season. They even have bugs to get after caterpillar.
I honestly can't tell because it seems like the spider mite damage continues . My humidity is very high when the lights are on so maybe it decreased the ipm mites.
Hi! When you say 'very high humidity' how high is that? Andersonii performs best 40%-80%, with 80% being the highest they will tolerate. Is it possible your humidity is too high?
Mite Matters
Thrips Have Six Stages. Cucumeris Reaches One.
A thrips passes through six life stages and cucumeris can kill one of them. Second instars do not just survive the attack — they fight it off, and they destroy the predator's eggs on the way past. That single fact explains the lag, the reservoir, and most of the disappointment.
Four Predatory Mites, Compared. Two of the Columns Are Guesses.
Every supplier prints the same four-column comparison table. We went and read the papers behind each cell. One column rests on unpublished company data, one species has never been trialled against thrips at all, and the humidity row is backwards. Here is that table with the guesses marked.
Your Cucumeris Are Alive. Your Thrips Are Winning.
Your mites are alive. Your thrips are also alive. That combination has twelve documented causes, and what the mites are doing — where they are, what they are sitting next to — narrows it to one or two in about five minutes.