Aphidius colemani is a slender, black insect with brown legs, long antennae and conspicuous wing venation. Its size depends on the size of the parasitized aphid, but is usually about 2 mm. The female has a pointed abdomen, while the male's abdomen is round-shaped.

The female Aphidius deposits an egg in an aphid. She bends her abdomen under her legs and injects an egg in the aphid with her ovipositor. This takes only a fraction of a second. The wasp parasitizes adults and nymphs. During the egg stage of the wasp (the first 3 days after parasitation), the aphid even eats more than normal and secretes more honeydew. Parasitized aphid adults or 4th instars keep on producing progeny.

Then, the Aphidius larva starts eating the aphid from inside, starting with the non-vital parts. Seven days after parasitation (at 21°C or 70°F) it fixes the aphid onto the leaf, and forms a silken cocoon which makes the aphid swell. The outside of the aphid becomes brown and leather-like, and is then called a mummy. Four days after the beginning of the mummification (at 21°C or 70°F) an adult Aphidius leaves the mummy through a round hole.

The total development of Aphidius colemani takes 14 days at 21°C (70°F), which is longer than aphid development in optimal circumstances (9 days). However, this is largely compensated by the hundreds of eggs Aphidius lays. The main part of these eggs is laid during the first 4 days. An adult Aphidius lives for 2-3 weeks.

The parasitic wasp finds aphid colonies from a long distance by "alarm signals" produced by an infected plant. At shorter distance it smells the honeydew. The adult Aphidius feeds on honeydew. At presence of an Aphidius in an aphid colony, aphids often secrete "alarm pheromones". The other aphids start to panic, and often let themselves fall down, and usually die on the ground.

Male Aphidius are born out of unfertilized eggs. These are deposited soon after mating or at the end of the female's life. The ratio females-males is usually about 2:1.

Several wasp species parasitize Aphidius larvae or pupae. A hyperparasite deposits an egg in the larva or young pupa of Aphidius. After hyperparasitation, the mummy stage takes place a few days longer than the usual four days for a non-parasitized Aphidius. Hyperparasites leave the mummy through a hole with a jagged edge, and not through a round hole as Aphidius does. Aphidius also usually leaves the lid attached to the exit hole.

Aphidius colemani can be released on all crops on which the compatible hosts occur. In view of the fast reproduction of aphids, they have to be controlled early. Aphidius colemani is very suited for preventative control. In several greenhouse crops, such as sweet pepper, cucumber, eggplant, rose and chrysanthemum, preventative weekly introduction of minimally 0.15 Aphidius/m² are recommended.

As soon as aphids are detected on catch plates (BUG-SCAN®) or on the plants, quantities are increased to 0.5-1 Aphidius/m²/week, depending on the crop and the situation, for at least 3 weeks.

In the case of a curative treatment often the gall midge Aphidoletes aphidimyza is released simultaneously. Further developed infestation are tackled with the ladybirds Adalia bipunctata, Harmonia axyridis or Hippodamia convergens, or with the selective pesticide pirimicarb (Pirimor, Rapid, ZZ-Aphox, ...). From summer on, aphid control with Aphidius colemani can be hampered by hyperparasites.

Aphidius colemani is supplied as mummies (parasitised aphids) packed per 500 pieces in plastic tubes. The mummies are mixed with saw dust. With this tube, the mummies can easily be sprinkled throughout the greenhouse. After delivery, the parasitic wasps have to be introduced as soon as possible.

If necessary, Aphidius colemani can be stored for a short while in a cool place (ca. 5°C, 41°F).

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