Impact of pest exclusion nets on bats in apple orchards

Abstract: Pest exclusion nets have recently been implemented in apple orchards to reduce the
use of insecticides and are unfolded before the emergence of the codling moth, the most
problematic pest. Recent studies have demonstrated that the presence of exclusion net can also impact other arthropod pests and their natural enemies. Here, we assess the effects of pest exclusion nets on insectivorous bats, which are major natural enemies of crop pests in apple orchards. We expected a lower bat activity per night in netted orchards due to a more intensive management (e. g., more frequent mowing), with a temporal effect of net deployment on bat activity per night in these orchards. We conducted a continuous acoustic survey of bats over a two-and-a-half-month period in organic apple orchards with (n = 15) and without (n = 12) pest exclusion nets in southeastern France. Global and guild-specific (functional group), bat activity per night were quantified in each orchard. Data collected during one week before and one week after net deployment in the netted orchards were extracted and used to conduct BACI (Before After Control Impact) analyses and compare bat activity per night in orchards with and without nets, before and after net deployment. Global and guild activities per night did not differ between netted and unnetted orchards in either period global and guild activities significantly declined in unnetted orchards after net deployment. More frequent insecticides applications in unnetted orchards may explain this pattern.