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

Jean-Charles Bouvier,Thomas Boivin,Claire Lavigne

doi:10.1007/s13593-021-00743-7

Abstract

Agricultural 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.

Highlights

Over the last decades, the processes of agricultural intensification, e.g., increased mechanization and pesticide use, expanded monocultures, and associated suppression of hedgerows, have been well associated with a dramatic global decline of breeding and wintering bird populations inhabiting farmed habitats (Donald et al 2001; EBCC 2020; Geiger et al 2010; Tscharntke et al 2005)
We investigated if C. pomonella single-row exclusion nets reduced abundance and species richness in bird assemblages in organic orchards and the extent of this reduction compared to integrated pest management (IPM) farming
This study provides the first assessment of the impact of an increasingly used pest exclusion technique on birds breeding in pome fruit orchards, one of the most extensive perennial crops worldwide

Summary

Introduction

The processes of agricultural intensification, e.g., increased mechanization and pesticide use, expanded monocultures, and associated suppression of hedgerows, have been well associated with a dramatic global decline of breeding and wintering bird populations inhabiting farmed habitats (Donald et al 2001; EBCC 2020; Geiger et al 2010; Tscharntke et al 2005). Across Europe, agricultural intensification has converted traditional fruit orchards with high natural value (Cooper et al 2007; Myczko et al 2013) into intensively managed, low-stem tree plantations that constitute more simplified habitats essentially managed to meet high production criteria (Simon et al 2010). Crop protection programs against pests in orchards mainly rely on synthetic (integrated pest management (IPM) farming) or natural (organic farming) pesticides (FAO 2009). Species abundance and diversity are generally significantly lower in IPM orchards than organic ones (Bouvier et al 2011; Genghini et al 2006; Katayama 2016; Wiacek and Polak 2008). Synthetic pesticides were negatively associated with bird reproductive success (Bishop et al 2000; Bouvier et al 2016; Fluetsch and Sparling 1994) and functional diversity through an attenuated representation of insectivorous species in the communities (Bouvier et al 2011; Genghini et al 2006; Katayama 2016; Wiacek and Polak 2008)

Methods

Results

Discussion

Conclusion