The aphid midge, and the one to reach for when you have more than one aphid at once or cannot identify the one you have. Aphidoletes aphidimyza takes over 60 aphid species — green peach, melon, potato, foxglove, cabbage, rose — and its orange larvae kill more than they need to eat.
It works while you are asleep and asks almost nothing of you. Nothing to mix, nothing to spray, no residue and no re-entry interval — you set the open container on damp shaded medium and the adults emerge over the following days, fly at night, find the colonies by scent and lay their eggs in among them. They reach aphid clusters tucked into growing tips a spray would never wet, and aphids cannot develop resistance to being eaten. Safe around people, pets and anything you plan to eat.
Two conditions decide whether it works indoors. It needs damp, shaded growing medium to pupate into, so the bottle goes low and on moist soil rather than onto foliage. And it reads day length: under roughly 13–15 hours the larvae enter diapause. A dim night light prevents that and it takes very little — under 5.5 lux — but it must not be red, and it will not override a cold room. They also need real darkness to fly and lay.
Best for: A moderate to heavy aphid infestation, several aphid species at once, or an aphid you cannot identify.
How many: Sizes go by square footage. Pairs well with Aphidius wasps — the wasps find the hidden aphids, the midge larvae clear the dense colonies.
Arrives as: Pupae in a wood fibre carrier in a ventilated bottle. Nothing will be moving, and nothing is supposed to be — adults emerge over the following several days.
Watch out for: Yellow sticky cards catch adult midges as efficiently as they catch pests, and ants will kill the larvae to protect their aphids. Deal with both before you release.
Safe around: People, pets, plants and food crops.
Not for: Anything that is not an aphid. The adults take only nectar and honeydew; it is the larvae that feed, and only on aphids.
Field Notes
Aphidoletes aphidimyza
The beneficial
Species
Aphidoletes aphidimyza
Common name
Aphid predator gall midge
Type
Predatory gall midge — generalist
Size
The larvae are tiny, bright orange to reddish and maggot-like — small, but easy to spot against a green leaf
How it works
The adults fly at night, locate an aphid colony by scent and lay their eggs in it. The larvae that hatch are the predators
What does the killing
The larvae. They paralyse the aphids and drink their body fluids
What it eats
Hunts
Aphids — over 60 species, among them green peach (Myzus persicae), melon or cotton (Aphis gossypii), potato (Macrosiphum euphorbiae), cabbage (Brevicoryne brassicae), foxglove (Aulacorthum solani), cannabis or hemp (Phorodon cannabis) and rose (Macrosiphum rosae)
Best against
A moderate to heavy infestation, or several aphid species at once — and the case where you cannot positively identify which aphid you have
Eats opportunistically
The adults take nectar and honeydew only. It is the larvae that eat aphids
What arrives
Format
Pupae in a carrier medium, inside a ventilated bottle. Nothing in the bottle will be moving and nothing is supposed to be. This one emerges over the following days — it does not get spread, and the carrier does not go onto leaves
Emergence
Adults emerge over several days, not all at once. Keep the release area slightly damp to assist it
Where it works
Optimal temp
Performs best between 68°F and 79°F. Activity slows significantly below 59°F
Humidity
High humidity is critical — 70% or higher — to stop the pupae and larvae drying out
Light
Sensitive to day length. Under roughly 13 to 15 hours the larvae enter diapause, so year-round indoor use needs supplemental light at night — and two details decide whether that works. It takes very little: under about 5.5 lux is enough. But it must not be red — in the study that established this, larvae did not respond to red light — and it does not override cold. At an 18°C day / 10°C night cycle the low light was nullified and 89% entered diapause anyway. They also need the dark: adults fly and lay at night, and a room on 24-hour lights gives them nowhere to do their job
Establishes
In a greenhouse with natural soil floors they may pupate in the soil and return, and left undisturbed with a moist pupation site they will run a second generation on their own. Bone-dry benches break the cycle after the first generation. In indoor tents or pots they usually do not persist
Running it
Deploy
The day of arrival. If a delay is unavoidable, a cool dark place at 40–50°F for no more than 48 hours
Placement
On damp, shaded growing medium — the open bottle, set down on moist rockwool or soil in a shaded spot near the base of infested plants, or in a release box. Not onto foliage and not onto dry soil. Set it low: midges emerge and fly up, so a container near the base puts the whole canopy above them
Release timing
At dusk or under low light. The adults are nocturnal and will start searching for egg-laying sites immediately
Replace
In indoor grow tents or pots, every 2–4 weeks during an active infestation
Compatible with
Aphidius wasps — the pairing professional growers use. The wasps find the hidden aphids while the Aphidoletes larvae clear out the dense colonies
Keep separate from
Yellow sticky cards, which catch adult midges as efficiently as they catch pests. And ants: they will kill Aphidoletes larvae to protect their aphid livestock, so deal with them first
Safe around
Humans and pets. Adults feed only on nectar and honeydew, and the larvae feed only on aphids
