Spotted Wing Drosophila in Sweet Cherry Orchards in Relation to Forest Characteristics, Bycatch, and Resource Availability.

Ernest Hennig,Dominique Mazzi

doi:10.3390/insects9030118

Abstract

Forest vegetation is essential for the population development of the spotted wing drosophila (SWD). Yet, little is known of how the structure of surrounding forest areas influence the abundance of SWD within orchards. In this work, we use data from a field trial at five sites in Switzerland to analyse the relationship between the extent of forest area, its edge density, and its distance from the orchard with the occurrence of SWD in sweet cherry orchards in a Bayesian hierarchical model. Availability of cherries and bycatch were also included in the model to account for effects of resource availability and trap attractiveness, respectively. For all main effects and their interactions, we accounted for potential temporal changes by adding interactions with time. We found that the closer an orchard was to a forest, the more SWD were trapped within the orchard. However, the interaction of forest proximity with forest area caused a disproportionate decrease of SWD catches. Also, the within orchard variables, trap catches of other drosophilid flies and resource availability affected SWD trap catches, but their relation changed in the course of the experiment. The findings imply that reducing SWD occurrence in orchards and other crop fields requires not only the consideration of processes outside and within the host crop field, but also of temporally changing relationships between SWD and other factors.

Highlights

Landscape composition surrounding crops plays an eminent role for insect pest species and their antagonists
We used a holistic approach for understanding spotted wing drosophila (SWD) colonization of sweet cherry orchards, analyzing forest distance and metrics at the landscape scale, and bycatch and resource availability at the local scale
SWD trap captures, but the interaction of forest proximity with forest area causes a disproportionate decline of SWD catches

Summary

Introduction

Landscape composition surrounding crops plays an eminent role for insect pest species and their antagonists. This role is generally advocated for antagonists (e.g., [1,2,3,4,5]), but it has been taken to a lesser extent into account for pests. Landscape structures such as forests, shrub vegetation and flowering field margins provide shelter, connectivity, alternative habitats, and food sources for pests [6,7]. In addition to the extent of landscape structures, their shapes can influence pest colonization of host crops. Complex structures can favour pest movement towards host crops by providing microhabitats that protect against unfavourable weather conditions and direct movement towards host crops [13]

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Discussion

Conclusion