Female wasps lay eggs in the aphid's body, which serves as a cocoon for the wasp pupa, known as a "mummy". These were collected from fruit trees and surrounding vegetation in several European countries and those that emerged were assessed for "production potential and parasitism efficacy", then tested on plants under laboratory conditions. Tubes of mummies from wasps showing promise were then tested in commercial cherry orchards in Belgium from the beginning of the growth season, with orchards then monitored weekly to quantify aphid infestation and parasitoid control.
"Mummies were found in abundance in the crop, which is an encouraging result," said the researchers. "However, full control of the aphids was not reached due to external factors that still need to be further investigated."
Comprising 27 partner organisations, the EUR12m (£9m) BIOCOMES project is working to develop a range of biological controls against pests and diseases. It runs until November 2017.