Description
Ervi Wasp- Aphidius ervi are tiny black wasps (4-5mm long) with long antennae and pointed abdomen, that parasitizes aphids. They are effective for large aphid species such as; Macrosiphum euphorbiae (Potato aphid), Aulacorthum solani (Foxglove aphid), Phorodon cannabis (Cannabis aphid), and Rhopalosiphum rufiabdominale (Rice Root Aphid)
The adult wasps have a highly efficient flight behavior and great at host location, providing good control if introduced early in season. Aphidius ervi is better adapted to cooler conditions than other Aphidius species.
The ideal temperature for development is 25-28°C. Parasitization is less effective at temperatures under 10˚C and over 30˚C. The life cycle is egg, 4 larval instars, pupae, then adult (14 days at 21°C). The females can produce over 300 eggs (mostly laid in first 3 days after emergence). The female deposits an egg in a live aphid where the four larval instars develop. Eggs hatch into larvae that consume the internal contents of aphids. The larva spins a cocoon inside the aphid cuticle, causing the swelled look of the “mummy”. The adult then exits the mummy through a round hole. The A. ervi pupal mummies are a leathery golden brown colour and can be identified from other aphid parasitoid wasps by their colour.
These wasp species are susceptible to hyperparasitization (another wasp species that lays its eggs inside the wasp larvae that is already laid inside the aphid). These hyperparasitoid wasps spontaneously enter the greenhouse in the summer and can seriously effect bio-control programs. Identification by the mummy is only possible after emergence of the adult (the hyperparasite leaves a jagged, irregular exit hole in the mummy). The Aphidius spp. leaves a round exit hole with a lid attatched on the posterior end of the aphid mummy.
