Effect of vegetational diversification on the gene flow of natural enemies in a plum orchard

Plant diversity strategies promote positive effects on the delivery of ecosystem services by establishing winter refuges and other food resources for populations of natural enemies. Cover crops are encouraged as a sustainable practice able to stimulate the early recruitment of natural enemies. However, there is insufficient evidence of the dispersal of natural enemies between added vegetation habitats and targeted crops in orchards. Here we study the genetic diversity and population genetic structure of a plum aphid parasitoid using microsatellite markers developed specifically for Aphidius platensis. We seek to understand whether parasitoid wasps are able to shift between alternative and target aphid hosts (winter vs. spring hosts) developing on winter oat cover crops, spontaneous vegetation, and the target plum trees in an organic orchard system. Our results supported aspects of our hypotheses by providing evidence that added habitat diversity, through a cereal cover crop, can act as banker plants of parasitoid populations for the dispersion of migrants within a fruit orchard, which could favor suppression efficiency of orchard pests, as well as enable population persistence of parasitoids.