Getting More Power from Your Flowers: Multi-Functional Flower Strips Enhance Pollinators and Pest Control Agents in Apple Orchards.

Alistair Campbell,Peter Sutton,Andrew Wilby,Felix Wäckers

doi:10.3390/insects8030101

Abstract

Flower strips are commonly recommended to boost biodiversity and multiple ecosystem services (e.g., pollination and pest control) on farmland. However, significant knowledge gaps remain regards the extent to which they deliver on these aims. Here, we tested the efficacy of flower strips that targeted different subsets of beneficial arthropods (pollinators and natural enemies) and their ecosystem services in cider apple orchards. Treatments included mixes that specifically targeted: (1) pollinators (‘concealed-nectar plants’); (2) natural enemies (‘open-nectar plants’); or (3) both groups concurrently (i.e., ‘multi-functional’ mix). Flower strips were established in alleyways of four orchards and compared to control alleyways (no flowers). Pollinator (e.g., bees) and natural enemy (e.g., parasitoid wasps, predatory flies and beetles) visitation to flower strips, alongside measures of pest control (aphid colony densities, sentinel prey predation), and fruit production, were monitored in orchards over two consecutive growing seasons. Targeted flower strips attracted either pollinators or natural enemies, whereas mixed flower strips attracted both groups in similar abundance to targeted mixes. Natural enemy densities on apple trees were higher in plots containing open-nectar plants compared to other treatments, but effects were stronger for non-aphidophagous taxa. Predation of sentinel prey was enhanced in all flowering plots compared to controls but pest aphid densities and fruit yield were unaffected by flower strips. We conclude that ‘multi-functional’ flower strips that contain flowering plant species with opposing floral traits can provide nectar and pollen for both pollinators and natural enemies, but further work is required to understand their potential for improving pest control services and yield in cider apple orchards.

Highlights

In the coming decades, agriculture must simultaneously meet the demands of feeding growing human populations while reducing its environmental impacts if we are to achieve goals for biodiversity conservation and food security [1]
We focused our observations on this period as floral resources for beneficial arthropods are more limited during the growing season (June until October) than prior to or during apple blossom [43]
We demonstrate that careful selection plant species based onstructures floral structures that determine we demonstrate that careful selection of plantofspecies based on floral that determine nectar nectar accessibility andflower insect flower visitation patterns beto used to design that attract accessibility and insect visitation patterns can becan used design flowerflower strips strips that attract both both pollinators and natural enemies inorchards, apple orchards, and enhance naturalactivity enemyinactivity in pollinators and natural enemies in apple and enhance natural enemy adjacent adjacent apple trees

Summary

Introduction

Agriculture must simultaneously meet the demands of feeding growing human populations while reducing its environmental impacts if we are to achieve goals for biodiversity conservation and food security [1]. Yield increases achieved using conventional farming practices (e.g., mechanisation, large field size, agrochemical usage) have come at a great cost to biodiversity [2,3,4], and generate negative feedbacks for biodiversity-mediated ecosystem processes that underpin crop yields (e.g., pollination, pest control, nutrient cycling), potentially undermining agricultural production [5,6]. Loss and fragmentation of flower-rich habitats (e.g., forest edges, grassland, hedgerows) has had negative effects on their populations in agricultural landscapes [11,12]. These non-crop habitats provide beneficial arthropods with more general benefits, in terms of shelter, nesting- and overwintering sites, that may be largely absent from modern agricultural systems [13,14,15,16]

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