Aphidius is a genus of tiny parasitic wasps (family Braconidae), about 2-3 mm long, that develop inside aphids. A female stabs an aphid with her ovipositor and lays one egg; the larva eats the aphid from inside, turning it into a bloated, papery, tan or golden "mummy". A new wasp chews a round exit hole and flies off to parasitise more aphids. They do not sting people.
In practice
Aphidius colemani targets smaller aphids such as green peach and melon aphids; Aphidius ervi handles larger species such as potato aphid. Matching the wasp to the aphid matters, so identify the species first. Growers release them preventively or at first sight of colonies, and some keep banker plants with grain aphids to breed wasps continuously. Mummies on leaves are the proof they are working. Wasps fly well and find scattered colonies that predators miss. Avoid broad-spectrum sprays and very high temperatures during releases.
Don't confuse with
- Aphid cast skins: white and flat, left after moulting; mummies are swollen and tan.
- Fungus-killed aphids: fuzzy and grey-white.
- Encarsia and Eretmocerus: parasitic wasps for whiteflies, not aphids.
