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 less than 15 hours they may enter diapause, so supplemental lighting for year-round indoor use. 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
