Amblyseius andersoni
A pale, droplet-shaped predatory mite about 0.5 mm long that eats many kinds of pest mite — spider, European red, russet, gall, broad and cyclamen mites — and lives on thrips, pollen and fungi when they are scarce. Its selling point is range: it is active from about 6 °C to 40 °C, so it can go in earlier in spring than other mite predators. It is a steady background predator for low numbers, not a cure for heavily webbed spider mite colonies.
At a glance
- Mode
- Generalist (polyphagous) predator of mites
- Rate
- 20–100 /m² (Biobest); 50–250 /m² weekly (Koppert); sachets 1 per 2 m of row
- Ships as
- Mites in bran with food mites, or breeding sachets
- Temp
- Active 6–40 °C; Koppert: effective above 14 °C, best 20–28 °C
- Humidity
- Above 65% RH (Koppert); US sellers give 50%+ or 60–90%
- Setting
- Greenhouse, tree nursery, ornamental and fruit crops
How it works
Biobest calls it polyphagous and lists its main targets as two-spotted spider mite, European red mite, apple rust mite and boxwood bud mite; it also eats thrips larvae — at 25 °C a female takes four to five first-instar western flower thrips a day (Koppert) — and it can live on pollen, honeydew and fungi. Because it has other food, it can go in before pests appear and hang on after they are gone, an advantage Biobest contrasts with predatory mites that prefer just one prey.
The limit is the webbing. Koppert markets it against non-webbing spider mites, and Dragonfli notes that it avoids webbing and does not like feeding on spider mites in high numbers — so suppliers advise adding Phytoseiulus persimilis on any hot spot. It occurs across the northern hemisphere, on apple, pear and maple (WSU). It is native to southern and western Europe, where it lives in vineyards and orchards, and WSU rates it the second most important predatory mite in European orchards after Typhlodromus pyri. Its reach down to about 6 °C is what lets it start work early in the season.
Is it established?
It is pale and small, and Koppert notes it cannot be told apart from related predatory mites by eye. Judge it by the pest mites on tagged plants, and by whether the sachets are still producing.
- DAY 1Pale, flat, droplet-shaped mites moving out of the carrier or sachet onto the leaves
- WEEK 1Tiny oval white eggs on leaf undersides, often in the angles of the veins
- WEEKS 2–4Pest mite counts steady or falling on the plants you tagged; no new webbed hot spots
- WEEKS 3–6Sachets stop producing; hang new ones if pests are still being found
Release & handling
Loose mites come in bran with food mites; breeding sachets contain a colony that keeps releasing predators for several weeks. It does not like cold storage: Biobest's ideal is 15 °C, Koppert and Bioline give 10–15 °C, and US sellers say do not refrigerate and release within 18 hours.
10–15 °C, never the fridge
Keep dark and ventilated (Koppert). Biobest says lower temperatures harm it. Release within 18 hours if you can.
Onto the leaves
Turn the container several times to mix, then sprinkle onto leaves and leave the carrier there for a few hours.
Hang in the canopy
Biobest: one sachet every 2 m of row. There is no need to open them.
Repeat
Loose mites weekly, at least three times (Koppert); sachets after four to six weeks. Add Phytoseiulus on hot spots.
Pesticide sensitivity
Pyrethroids, organophosphates and carbamates can be toxic to predatory mites (UMN). Tolerance varies by strain: in Italian apple orchards, wild andersoni populations were unaffected by repeated pyrethroid sprays, while in the lab one commercial strain died on deltamethrin and others survived. Check a product →
When to choose something else
Andersoni is a broad, cold-tolerant background predator. Choose something else when:
- Spider mites are already webbing plants — andersoni avoids the webbing; suppliers pair it with Phytoseiulus persimilis on hot spots
- The crop is tomato — Koppert says not to use it there, as the leaf hairs stop it establishing (Bioline does list tomato russet mite as a target)
- Thrips are the main problem — Koppert sells it against young thrips larvae, but Biobest treats thrips as extra food; compare a dedicated thrips predator
- The air is very dry — Koppert says it is sensitive below 65% relative humidity
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics25,000 to 125,000; sachetsUS
- Biobest (Andersoni-System)25,000 tube; 250 sachetsEU / NA
- Bioline AgroSciences (Anderline)2,000 to 125,000; sachetsUK / NA
- Buglogical25,000; 62,500 in 250 sachetsUS
- Koppert (Anso-Mite, Anso-Mite Plus)125,000 bucket; sachetsGLOBAL
- Sound Horticulture2,000 to 250,000; sachetsUS