Stratiolaelaps scimitus
Sold for years as Hypoaspis miles, and still searched under that name: a tan, soil-dwelling predatory mite under 1 mm long that lives in the top centimetre or two of moist compost. It eats fungus gnat eggs and young larvae, thrips pupae and springtails, and scavenges on debris and algae when prey runs short, so it stays in the compost for weeks. It is a preventive, put in at potting before numbers build — not a quick fix for a pot already full of larvae.
At a glance
- Old name
- Hypoaspis miles
- Size
- Under 1 mm; tan to brown
- Rate
- 100–500 /m² (Biobest: 50–1,000)
- Temp
- Media above 15 °C (Biobest: 10 °C)
- Lives in
- Top 1–4 cm of moist compost
- Without prey
- About 4–7 weeks; scavenges debris and algae
How it works
The mite hunts in the surface layer of the compost — UConn puts it in the top 1.3 cm, Biobest in the top 1–4 cm. It feeds on fungus gnat eggs and first-stage larvae, thrips prepupae and pupae, springtails and shore fly larvae, and when prey is scarce it scavenges on plant debris and algae. That is what makes it a preventive: Biobest says it can live up to seven weeks without food and Dragonfli about four, so it can go in before the pest arrives and still be there when it does.
The limits follow from the same habit. It stays in the compost and very rarely goes onto the plant, so it does not reach adult gnats or the thrips larvae feeding in the flowers, and it only reduces the next generation. It needs moist compost, ideally loose and rich in organic matter (Koppert); it does not survive standing water or flooding, and Biobest says the medium must not dry out. Koppert describes the reduction as slow but steady, which is why UConn advises pairing it with nematodes or Bti once gnats are already established. Sources also disagree on shore flies: UConn and Biobest list shore fly larvae as prey, while Buglogical and Evergreen say it does not control them.
Is it established?
What a working release looks like. Check the compost, not the flies: adults already pupating will keep emerging for a while.
- DAY 1Tan, fast-moving mites on the compost surface; the slow, whitish mites in the carrier are their food
- WEEK 1Fewer larvae under potato slices; Dragonfli says re-apply if numbers have not fallen after seven days
- WEEKS 2–3The usual point for a second release if gnats persist
- AFTERMites still found in the top 1–2 cm of compost while it stays moist
Release & handling
The mites arrive live in a bottle of peat, bran or vermiculite, with food mites to keep them going. Do not refrigerate them. Koppert says to use them as soon as possible and store them for 1–2 days at most, at 10–15 °C, in the dark with the bottle on its side; US retailers range from Arbico's "use within 18 hours" to a week (Buglogical) or two (Evergreen) at room temperature.
Cool, dark, on its side
10–15 °C (Biobest: 12–18 °C). Never in the fridge. Use within a day or two.
Moist compost
Water first so the media is moist, not wet. The mites do not survive standing water.
Turn, then sprinkle
Rotate the bottle to mix the mites through the carrier, then sprinkle evenly on the surface, not against the stems. UConn and Evergreen say not to mix it into the compost, though Arbico allows mixing it in at potting.
Leave the bottle
Stand the open bottle in the crop so stragglers can walk out. Treat under benches too, where gnats breed.
Pesticide sensitivity
Biobest says it can go in alongside insect-parasitic nematodes. Check the supplier's side-effects list before any drench or spray that reaches the compost. Check a product →
When to choose something else
A standing guard in the compost, not a rescue. Choose something else when:
- Larvae are already numerous — drench Steinernema feltiae, or use this mite with nematodes or Bti as UConn advises
- It is a single houseplant in a home — UC IPM says Hypoaspis probably won't perform well there; dry the surface and use yellow cards
- Compost is below 15 °C — Koppert and UConn give that as the working minimum
- Plants sit in waterlogged or flooded media — it does not survive flooding, and Koppert wants moist, loose compost rich in organic matter
- The damage is thrips on flowers and leaves — it only meets the pupae, so a foliar predator must do the main work
Where to buy
Suppliers listed alphabetically, not ranked. Some still sell it as Hypoaspis miles. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics12,500 / 25,000 / 50,000 / 125,000US
- Biobest (Hypoaspis-System)10,000 / 25,000 / 125,000EU / NA
- Buglogical25,000 to 100,000US
- Dragonfli2,000 to 50,000UK
- Evergreen Growers Supply25,000 per bottleUS
- Koppert (Entomite-M)10,000 / 50,000 / 125,000GLOBAL
Stratiolaelaps scimitus by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.