Wildflower plantings on fruit farms provide pollen resources and increase nesting by stem nesting bees

Abstract

Wildflower plantings on farms have been shown to attract foraging wild bees, however, whether these added floral resources increase nesting densities of bees remains largely untested. 2 We placed nest boxes containing natural reeds at 20 fruit farms in Michigan. We then compared nesting densities between farms with and without wildflower plantings and analysed nest provisions to evaluate use of wildflower plantings for brood provisioning. 3 We found significantly greater nesting at farms with wildflower plantings, with only one out of 236 completed nests at a farm without a planting. The majority of nests were completed by Megachile pugnata, with a portion of nests completed by Osmia caerulescens. 4 We found that nesting bees collected pollen from only a subset of the available flowers in the wildflower plantings, with a strong preference for Centaurea maculosa, and Rudbeckia type pollens. While these species were found growing in the plantings, only Rudbeckia type species were seeded in the plantings. 5 This study provides evidence that wildflower plantings (though not only seeded species) are filling a critical resource gap for stem-nesting bees in agricultural landscapes and likely support local populations.

Biology, Genetic Diversity, and Conservation of Wild Bees in Tree Fruit Orchards

“…Increases in wild bee visitation and the setting of fruit were linearly correlated with an increase in wild bee habitat in fruit orchard [251]. In summary, an increase in nesting density with wildflower planting fulfills the critical resources for bee conservation in orchard agroecosystems [252][253][254].…”

“…Open grassy areas around the apple orchard are better predictors for wild bees visiting apple orchards than 'natural vegetation' or an 'open grassy area plus natural vegetation' [320]. There was greater bee nesting at farms with wildflower planting compared with farms without planting [254]. The preference for nesting bees was predominantly for few subsets of available flowers (Centaurea maculosa and Rudbeckia) rather than most mixed wildflower plants [254].…”

“…There was greater bee nesting at farms with wildflower planting compared with farms without planting [254]. The preference for nesting bees was predominantly for few subsets of available flowers (Centaurea maculosa and Rudbeckia) rather than most mixed wildflower plants [254]. In cherry orchards, landscape management with a semi-natural habitat and increased native flowering plants increases wild pollinator diversity, which results in the support setting of cherry fruit [321].…”

How effective are artificial nests in attracting bees? A review

“…Martínez-Núñez et al (2020) found that organic fields had higher colonization rates than their control farms. Graham et al (2020) found that significantly greater nesting at farms with wildflower plantings, with only one out of 236 completed nests at a farm without a planting. Guisse and Miller (2011) found that nest number per site was positively correlated with proximity to water, but negatively with elevation.…”

Pollinator planting establishment and bee visitation are influenced by seeding rate and post‐seeding management

“…These plantings are installed to provide nutritional and nesting resources for pollinators throughout the season, which help to promote pollinator diversity and abundance on local (Garibaldi et al 2014; Lowe et al 2021; Scheper et al 2021) and landscape (Jönsson et al 2015) scales. This conservation practice can be incorporated into farms to support bees and other pollinating insects (Carvell et al 2021; Graham et al 2021), as well as natural enemies (Blaauw & Isaacs 2015; Campbell et al 2017; Hatt et al 2017), and birds (Pywell et al 2012). Furthermore, wildflower plantings may benefit surrounding natural systems through soil stabilization (Bretzel et al 2009), reduction of pesticide and fertilizer run‐off (Aldrich 2002; Wratten et al 2012), and increased carbon sequestration (Weißhuhn et al 2017; Ruf & Emmerling 2020).…”