Single-row exclusion nets: an alternative pest control method with no detectable impact on breeding bird assemblages in orchards bordered by hedgerows

Abstract

AbstractAgricultural intensification has led to dramatic declines in bird populations. In particular, the acknowledged role of synthetic pesticides on direct bird intoxication or food resource depletion urges us to seek alternative crop protection methods. Pest exclusion netting systems have recently gained popularity among fruit growers as an efficient means of reducing pest attacks, allowing their transition to organic farming. Single-row exclusion nets, which only cover fruit trees and leave uncovered both the inter-row grassy strips and the hedges, are increasingly being used in apple orchards of Southern Europe. However, net-induced effects on wildlife remain unknown. This study is the first to assess the impacts of single-row exclusion nets on breeding bird communities. We hypothesized that the exclusion net effects would be weaker than those associated with synthetic pesticide use, except for bird species that forage in the tree canopy. We monitored breeding bird abundance, and species richness in 46 commercial apple orchards managed using integrated pest management (IPM) or organic standards with or without exclusion nets. We counted 705 birds belonging to 32 different species. Total bird abundance, the number of observed species, and the Chao1 estimate of species richness were influenced by orchard management strategy. Breeding bird assemblages in organic orchards were as numerous and diverse in both the presence and absence of exclusion nets. In contrast, both bird abundance and species richness were significantly decreased in IPM orchards. The abundance and species richness of bird assemblages and the abundance of a few individual species also increased with the number of hedgerows bordering the orchards. Our results demonstrate that single-row netting systems for organic farming represent an effective pest control strategy with no significant impact on bird communities and highlight the importance of hedgerows along the orchards’ edges.