Abstract
Wild bees provide a free and potentially diverse ecosystem service to farmers growing pollination-dependent crops. While many crops benefit from insect pollination, soft fruit crops, including strawberries are highly dependent on this ecosystem service to produce viable fruit. However, as a result of intensive farming practices and declining pollinator populations, farmers are increasingly turning to commercially reared bees to ensure that crops are adequately pollinated throughout the season. Wildflower strips are a commonly used measure aimed at the conservation of wild pollinators. It has been suggested that commercial crops may also benefit from the presence of noncrop flowers; however, the efficacy and economic benefits of sowing flower strips for crops remain relatively unstudied. In a study system that utilizes both wild and commercial pollinators, we test whether wildflower strips increase the number of visits to adjacent commercial strawberry crops by pollinating insects. We quantified this by experimentally sowing wildflower strips approximately 20 meters away from the crop and recording the number of pollinator visits to crops with, and without, flower strips. Between June and August 2013, we walked 292 crop transects at six farms in Scotland, recording a total of 2826 pollinators. On average, the frequency of pollinator visits was 25% higher for crops with adjacent flower strips compared to those without, with a combination of wild and commercial bumblebees (Bombus spp.) accounting for 67% of all pollinators observed. This effect was independent of other confounding effects, such as the number of flowers on the crop, date, and temperature. Synthesis and applications. This study provides evidence that soft fruit farmers can increase the number of pollinators that visit their crops by sowing inexpensive flower seed mixes nearby. By investing in this management option, farmers have the potential to increase and sustain pollinator populations over time.
Highlights
In the past few decades, populations of both domestic and wild honey bees have fallen dramatically in some countries such as the UK and USA (Kremen et al 2004; Potts et al 2010)
Sixty-seven percent of the pollinators observed across all transects belonged to the genus Bombus (58% B. terrestris/lucorum, 4% B. lapidarius, 3% B. pratorum, and 2% B. pascuorum)
Hoverflies were slightly more abundant in treated crop polytunnels (2.84 Æ 0.46 per 100-m transect) than in controls (2.31 Æ 0.44), with the inverse being true of honeybees, which were more likely to be observed on control transects than treated transects (0.61 Æ 0.13 and 0.21 Æ 0.07 per 100-m transect, respectively); both honeybees and solitary bees were poorly represented on crop transects relative to Bombus spp. and Syrphidae spp
Summary
In the past few decades, populations of both domestic and wild honey bees have fallen dramatically in some countries such as the UK and USA (Kremen et al 2004; Potts et al 2010). Agricultural intensification is believed to be one of the key drivers of these declines (Goulson et al 2008), but while modern agriculture may represent a hostile environment for pollinators, the number and extent of crops requiring pollination have increased. Insect pollination has been conservatively calculated to be worth around $3.07 billion per annum in the United States alone (Losey and Vaughan 2006) making pollinator declines concerning when considering the sustainability of our food production systems (Biesmeijer et al 2006; Aizen et al 2008; Aizen and Harder 2009; Goulson 2003; Potts et al 2010; Ollerton et al 2011).
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