Parasitic wasp

Aphidius ervi

Aphidius ervi looks very similar  to A. colemani and attacks aphids in the same way. However, A. ervi tends to prefer larger aphid species, including the potato aphid (Macrosiphum euphorbiae), foxglove aphid (Aulaconhum solani) and cannabis aphid (Phorodon cannabis); its host range does include some smaller aphid species, however, and adults that emerge from these hosts will be somewhat smaller than those emerging from larger aphids. The largest adults are typically about 2.5—3 mm long, with dark bodies and legs.

The optimal temperature for this species is approximately 25°C (77°F),  it can still be effective at 20°C (68°F), but at Iower temperatures (15°’C or 59 °F), both survival and parasitism levels are reduced. Survival is also reduced at temperatures of 30°C (86°F) or higher. The life-cycle (egg to adult) takes approximately 10—12 days at 25 °C (77°F), with males generally emerging slightly earlier than females.

Note that the immature stages of both A ervi and A. colemani can be attacked by other naturally occurring parasitic wasps while developing inside host aphids; even in
greenhouses, these ‘secondary’ or ‘hyperparasitoids’ can gradually increase over the growing season and may eventually reduce the effectiveness of Aphidius. If this occurs, it may be necessary to introduce another aphid biological control agent (such as Chrysoperla rufilabris or Aphidoletes aphidimyza).