Honey bee stocking numbers and wild blueberry production in Nova Scotia

Abstract

Eaton, L. J. and Nams, V. O. 2012. Honey bee stocking numbers and wild blueberry production in Nova Scotia. Can. J. Plant Sci. 92: 1305–1310. Wild blueberries (Vaccinium angustifolium Ait.) require cross pollination by insects. Introduction of managed species such as honey bees (Apis mellifera L.) and alfalfa leafcutting bees (Megachile rotundata Fabr.) is costly. We assessed the effects of stocking rates of honey bee hives and the interacting effects of the numbers of honey bees and other bees on yield of blueberries in commercial fields. Blueberry fields were sampled from 101 fields in years 1991 to 2010 in Nova Scotia. We recorded field size, numbers of beehives, yield, densities of bees, numbers of buds, blossoms and set fruit. Yields increased linearly with numbers of beehives, up to∼4 hives/hectare, but at higher stocking rates there was too much variation to adequately determine the effects. Yields also increased linearly with numbers of honey bees, but there was an interaction with other bees that decreased the effects of honey bees, such that at maximum densities of other bees, there was no effect of honey bees on yield. These results suggest that other bees and honey bees compete for pollination. If producers have limited numbers of beehives, we suggest that more should be placed in areas where densities of other bees are lower, up to approximately 4 hives/hectare.

Wild bee pollinator communities of lowbush blueberry fields: Spatial and temporal trends

“…Consequently, lowbush blueberry can probably depend on wild pollinators more than any other crop in North America. It is estimated that over one quarter of lowbush blueberry fields in Nova Scotia can receive adequate pollination from wild species alone (Eaton & Nams 2012). In other words, growers may reap significant pollination service without having to rent or buy managed honey bee colonies.…”

A global review of arthropod-mediated ecosystem-services in Vaccinium berry agroecosystems

“…Bushmann (2013) over a three-year period (2010-2012) demonstrated a strong response between fruit set and honey bee and native bee visitation rates, acting independently. Two other recent studies in Maine and Nova Scotia have documented similar relationships between bee density/activity and fruit set and yield (Asare, 2013;Eaton and Nams, 2012).…”

Where is the value in valuing pollination ecosystem services to agriculture?

“…A recent survey of blueberry growers registered this disconnection; the widely perceived benefits of wild pollinators do not translate into investment in habitat conservation, but rather inexpensive and passive changes to farm management practices, such as withholding insecticide sprays during bloom (Hanes et al, 2013). Notably this is for a crop in which wild pollinators have been estimated to provide sufficient pollination across 25% of farms (Eaton and Nams, 2012). While investment has stubbornly resisted habitat protection initiatives, it has readily been available for the rapid expansion of commercially produced Bombus impatiens colonies, a species which is superior to honey bees for pollinating blueberries (Desjardins and De Oliveira, 2006;Drummond, 2012) but whose introduction is implicated in harming wild Bombus spp.…”

“…There is also evidence of interaction effects, in which the pollination efficacy of honey bees is enhanced greatly by the presence of high densities of wild bees Greenleaf and Kremen, 2006). Furthermore, in a number of commercial cropping systems, wild bee densities seem sufficiently high to render the rental of honey bee colonies superfluous (Eaton and Nams, 2012;Petersen et al, 2013;Winfree et al, 2007;Winfree et al, 2008). Despite these demonstrated benefits, the value of wild bees to agriculture, and their value relative to managed honey bees, is simply not reflected in current valuation estimates at either national or global scales.…”