Preliminary results on the effect of the creation of vegetation islandswith flowering plants on beneficial insects associated with the olive agroecosystem

Abstract: The effective conservation of natural enemies of crop pests involves manipulation ofthe environment to favor their role, namely by providing sources of plant-derived foods such asnectar, pollen, or both, which can in some cases enhance the survival and reproduction of thesebeneficials. This work reports preliminary results of a study on the effect of the creation ofvegetation islands with flowering plants on the populations of beneficial insects associated withthe olive agroecosystem, with emphasis to the natural enemies of Prays oleae (Bern.). Threetreatments were compared: uncovered soil, soil sown with buckwheat (Fagopyrum esculentumMoench) alone or with a mixture of wild carrot (Daucus carota L.). The insect populations ineach plot were monitored by sticky traps over eight weeks. Furthermore, a sample of larvae andpupae of P. oleae was collected from the three treatments at the end of the fruit generation (inSeptember) and the rates of parasitism were evaluated. The number of either Hymenopteraparasitoids or Coccinellidae captured differed significantly between treatments, with the highervalues in the “buckwheat” plots and the lower in the “uncovered soil” plots. About 70% of thecaptures were obtained during the “full flowering” period of the tested plants. However theparasitism rates of larvae and pupae of P. oleae although higher in the “buckwheat” plots incomparison to the other ones, did not differed statistically among them.