Feltiella acarisuga
A tiny, delicate gall midge whose larvae live inside spider mite colonies and suck the mites dry — eggs, young and adults. The larvae are orange and about 2 mm long when grown. It is sold as pupae in a bottle, and the adults fly out to find mite colonies on their own. It is a hot-spot tool, released weekly from the first hot spots, alongside Phytoseiulus persimilis. It does best in warm, humid air: Koppert gives 68–81 °F (20–27 °C) and above 80% relative humidity.
At a glance
- Mode
- Predator — only the larvae feed
- Rate
- 0.25–25 /m², weekly, 3+ times
- Ships as
- 250 pupae in a bottle
- Temp
- 68–81 °F (20–27 °C)
- Humidity
- Above 80% (Koppert); UC: above 60%
- Egg to adult
- About 15–17 days in warmth
How it works
The adult midge does not hunt. It lives on water and sugar and searches out spider mite colonies, laying its eggs on leaves and webbing in and around spider mite colonies. The larva that hatches is yellowish white, turning orange, red or yellow depending on what it eats. It pins its prey, sucks out the contents and leaves only empty skins. Koppert puts a larva's intake at 15 adult mites or up to 50 mite eggs a day. A life-table study that fed larvae only mite eggs measured more: 38, 60 and 87 eggs a day on average across the three larval stages. In a laboratory comparison, a larva took up to 50 eggs a day, against 25.6 for Neoseiulus californicus and 15.1 for the Swirski mite. Koppert adds that the larvae will also eat spider mites that have gone into winter rest.
Development is quick in warmth. At 80 °F (26.7 °C), egg to adult took 17.4 days in one life-table study, and Arbico gives about 15 days. Larval feeding lasts 4–6 days by Arbico's figures, 7.8 days in the life-table study; the larva then spins a white cocoon on the underside of a leaf, usually along a vein. A 2021 temperature study put its lower development threshold at 47 °F (8.2 °C), and judged 76–84 °F (24.5–28.7 °C) the most suitable range for its development. Biobest adds that it stays active in cooler, low-light spells in spring and autumn. Dry air is its weak point: UC IPM notes that low humidity cuts egg-laying and larval and pupal survival. Because the female seeks out colonies, it works best where mites are clustered, which is why it goes on hot spots.
Is it established?
What a working release looks like. Look inside the mite colonies, not on the open leaf: the larvae sit among the webbing.
- DAYS 1–14Adults emerge from the bottle; leave it in the crop for at least two weeks
- DAYS 3–10Tiny yellowish-to-orange larvae inside the colonies, among empty, shrivelled mites
- DAYS 7–14White cocoons on leaf undersides, usually along the veins
- WEEKS 2–3A new generation of midges; colonies thin out. Keep releasing weekly for at least three weeks
Release & handling
Pupae arrive in a small bottle, or on leaves from some US suppliers. Release on arrival. Koppert allows 1–2 days at 54–57 °F (12–14 °C) in the dark, and Arbico says use within 18 hours and never refrigerate.
Cool, dark, not the fridge
54–57 °F (12–14 °C) for 1–2 days at most (Koppert).
Upright, in the hot spot
Stand the open bottle in the crop, on the ground or a rockwool slab, near the worst colonies.
Sugar water in the cap
Koppert: leave the cap nearby with sugar water for the emerging adults.
Shade and dry
Keep the bottle out of direct sun and irrigation, and leave it for two weeks.
Pesticide sensitivity
No side-effect ratings for this midge were found in the extension sources read for this page. Check the supplier's side-effects list before any spray, and treat broad-spectrum insecticides as harmful. Check a product →
When to choose something else
A fast, mobile predator for spider mite colonies in humid glasshouses. Choose something else when:
- Mites are still scattered and few — Neoseiulus californicus is the preventive predator
- You need the main workhorse against two-spotted spider mite — Phytoseiulus persimilis, which Koppert pairs this midge with
- The air is dry — UC IPM gives above 60% humidity as optimal, and in dry air egg-laying and larval and pupal survival fall sharply
- It is outdoors in dry heat — the spider mite destroyer beetle is rated for 30–90% humidity (Arbico)
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics250 (pupae on leaves)US
- Biobest (Feltiella-System)Cup of pupaeGLOBAL
- Koppert (Spidend)250 pupae / bottleGLOBAL
Feltiella acarisuga by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.