Non-intended effects of exclusion nets on predatory and herbivorous arthropods at local and landscape scales

Abstract: In recent years, alternative pest-control strategies aiming to reduce pesticide use have expanded, although their non-intended effects remain poorly documented. This is particularly true for insect-exclusion nets in perennial cropping systems, where effects may occur at both local and landscape scales. In 2021 and 2022, we monitored 17 pairs of organic apple orchards in south-eastern France, either protected by nets or not, to disentangle local and landscape-scale effects of nets on canopy-dwelling predatory and herbivorous arthropods. At the local scale, netted orchards exhibited higher predator abundance and predator–herbivore ratio compared to non-netted orchards, while herbivore abundance remained unaffected. At the landscape scale, a higher proportion of nets was marginally associated with increased herbivore abundance and a reduced predator/herbivore ratio, with no interaction with local effects of nets. Overall, these results suggest that insect-exclusion nets may represent a viable agroecological strategy with limited non-intended effects.