Non-target effects of exclusion nets on pests in apple orchards

Abstract: Alternative pest management strategies can produce non-target effects on pests, yet
these effects remain poorly understood. Apple orchards face strong pest pressure, with the
codling moth, the rosy and woolly apple aphids, and the Mediterranean pine vole among the
most damaging species. In recent years, Alt’Carpo nets, which are highly effective against the
codling moth, have become widely used in French apple orchards. Understanding how this
practice influences target and non-target pest species is crucial for preventing damage and
ensuring sustainable orchard management. From 2021 to 2023, we monitored key pests in 46
commercial organic apple orchards, with and without nets, within the Lower Durance Valley in southeastern France. Our surveys showed that nets exert not only local effects, but also broader landscape effects by redistributing populations of some pests. A higher proportion of netted orchards in the landscape increased codling moth and rosy apple aphid pressure in unnetted orchards, while reducing the presence of voles in those same orchards. Conversely, the presence of a net locally tended to buffer the orchard from landscape effects.