Bayesian inferences of arthropod movements between hedgerows and orchards

Abstract

Hedgerows are agro-ecological infrastructures that are assumed to enhance biodiversity in an agro-ecosystem and the control of crop pests. However, local movements of arthropod predators from hedgerows to crops remain poorly understood. In this research, these movements were analysed in eleven commercial apple orchards over two weeks in the spring of 2014. Predators were indirectly marked by spraying ovalbumin on the hedgerows. Canopy and ground predators were captured using beating and pitfall traps, respectively, in both the orchards and the hedgerows, and individuals marked by ovalbumin were detected using ELISAs. Approximately 20% of the 1272 captured predators were identified as marked. Movements between the orchards and the hedgerows of the most abundant predator taxa (Forficula auricularia, Chrysoperla sp., Philodromus spp., Cheiracanthium mildei, and Nebria brevicollis) and of four guilds (ground spiders, ground beetles, canopy spiders and canopy insects) captured across the eleven locations were estimated using a Bayesian model. On one hand, canopy insects and ground spiders were less likely to stay in the hedgerows than were the canopy spiders and ground beetles. On the other hand, the canopy spiders and ground beetles were less likely to stay in the orchard than were the canopy insects and ground spiders. However, there were exceptions within these groups: F. auricularia and N. brevicollis exhibited a high probability of staying in the hedgerow and in the orchard, respectively. Overall, these results demonstrate the frequent movements that occurred between the orchard and the adjacent hedgerow in a diverse range of predator taxa. The probabilities of movement were further affected by the characteristics of the orchard for most taxa. Therefore, agro-environmental measures that focus on hedgerow management require consideration of the local arthropod predator communities and their characteristics to enhance pest control in apple orchards.