Study of two conditioning methods of parasitoids used in biological control prior to inundative releases in apple orchards

  • Valérie-Anne Dumont Earth and Life Institute, Biodiversity Research Centre, 4–5 Place Croix du Sud, 1348 Louvain-la-Neuve (Belgium), +3210443700
  • Antoine Trigaux Earth and Life Institute, Biodiversity Research Centre, 4–5 Place Croix du Sud, 1348 Louvain-la-Neuve (Belgium), +3210443700
  • Anaïs Moreau Earth and Life Institute, Biodiversity Research Centre, 4–5 Place Croix du Sud, 1348 Louvain-la-Neuve (Belgium), +3210443700
  • Thierry Hance Earth and Life Institute, Biodiversity Research Centre, 4–5 Place Croix du Sud, 1348 Louvain-la-Neuve (Belgium), +3210443700

Abstract

The rosy apple aphid, Dysaphis plantaginea Pass., is a major pest in apple orchards in Belgium. Two micro-hymenopteran parasitoids Aphidius matricariae Haliday and Ephedrus cerasicola Stary are potentially capable of controlling this pest. However, when released in orchards the adult parasitoids tend to disperse. Based on the results of previous work it is proposed that the reason is that the artificial diet in which they are raised does not contain the odors that enable the parasitoids to identify the habitat where there are suitable aphid hosts. To optimize the control and make it economically effective it is important to reduce dispersal. This might be done by conditioning parasitoids during rearing by exposing them to the odors associated with orchards. The odor used in this study was a hydrodistillate of apple leaves, the main host-plant of the targeted aphid. Two methods of conditioning were used: 1) soaking mummies of the parasitoid in pure hydrodistillate, 2) including a defined concentration of hydrodistillate in the artificial diet used for rearing the parasitoid. They were exposed to either a dilution of 100x, 200x and 1000x in two consecutive generations. The response of adult parasitoids to odors was determined using a dual choice olfactometer. Of the E. cerasicola conditioned by soaking the mummies 70-75% of individuals were attracted to the odor of plants infested with D. plantaginea compared to the 55-60% in the controls. The A.matricariae that were conditioned by feeding them artificial diets containing different concentrations of apple odor for one or two generations, showed no preference for the odor of apple leaves. Second generation adults of E. cerasicola exposed to a 200 times dilution of pure hydrodistillate showed a more marked response to apple odor.

Published
2011-11-06
Section
Articles