Orchard Pollination in Capitol Reef National Park, Utah, USA. Honey Bees or Native Bees?

Authors: Tepedino, Vincent; ALSTON, DIANE - Utah State University; BRADLEY, BROSI - UNAFFIL.,HUNTINGDON,PA; TOLER, TRENT - UNAFFILLIATE,HYRUM,UT; Griswold, Terry

Submitted to: Biodiversity and Conservation Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2006
Publication Date: 10/1/2007
Citation: Tepedino, V.J., Alston, D.G., Bradley, B.A., Toler, T.R., Griswold, T.L. 2007. Orchard Pollination in Capitol Reef National Park, Utah, USA. Honey Bees or Native Bees? Biodiversity and Conservation. 16(1)3083-3094.

Interpretive Summary: Unlike most National Parks in the United States, Capitol Reef National Park in central Utah includes an agricultural component. The Park surrounds 22 orchards of apples, pears, sweet cherries, apricots and other crops started over a century ago by Mormon pioneers. During bloom, hives of the introduced honey bee are brought into the Park to pollinate the orchard crop flowers although the area in which the Park is embedded has over 700 species of native bees, some of which may be potential crop pollinators. We conducted observations and collections of insects visiting the flowers of four orchard crops (apple, pear, apricot, sweet cherry) over two years to describe the role that native bees are playing in pollination. We collected 30 species of bees visiting the four crops; except for pear flowers in one orchard, most native bees were uncommon. Flowers are currently being pollinated mostly by honey bees. Evidence that honey bees were preventing native bees from foraging on the orchard crop flowers was mixed: absence of competition between honey bees and native bees was suggested by the absence of a significant correlation between honey bee and native bee visitation rates to the flowers, or between native bee visitation rates and distance from honey bee hives. On the other hand, competition was suggested by the consistently larger numbers of honey bees on the flowers, and the increase of native bees in one pear orchard in response to low honey bee numbers. Approximately one-third of the native bee species captured on the flowers are potential pollinators. This includes species that nest in holes in wood such as the blue orchard bee, Osmia lignaria propinqua, which is currently managed commercially for small orchard pollination in the United States. Several other more generalized flower-visitors and one (Andrena milwaukiensis) which prefers flowers in the rose family (all orchard crops studied are in that plant family), are all potentailly important orchard crop pollinators. We recommend that honey bees be withdrawn gradually from the Park to allow native bees to increase and pollinate these orchard crops.

Technical Abstract: Unlike most National Parks in the United States, Capitol Reef National Park in central Utah includes an agricultural component. The Park surrounds 22 rosaceous fruit orchards started over a century ago by Mormon pioneers. During bloom, hives of the alien honey bee are imported to pollinate the flowers although the area in which the Park is embedded has over 700 species of native bees, some of which may be potential crop pollinators. We conducted observations and collections of insects visiting the flowers of four orchard crops (apple, pear, apricot, sweet cherry) over two years to describe the role that native bees are playing in pollination. We collected 30 species of bees visiting the four crops; except for pear flowers in one orchard, most native bees were uncommon. Flowers are currently being pollinated mostly by honey bees. Evidence that honey bees were preventing native bees from foraging on the orchard crop flowers was mixed: absence of competition was suggested by the absence of a significant correlation between honey bee and native bee visitation rates to the flowers, or between native bee visitation rates and distance from honey bee hives. On the other hand, competition was suggested by the consistently larger numbers of honey bees on the flowers, and the increase of native bees in one pear orchard in response to low honey bee numbers. Approximately one-third of the native bee species captured on the flowers are potential pollinators. This includes cavity-nesting species such as the blue orchard bee, Osmia lignaria propinqua, which is currently managed commercially for small orchard pollination in the United States, plus several other generalized foragers and one apparent specialist forager of plants in the Rosaceae (Andrena milwaukiensis) that are fossorial. We recommend that honey bees be withdrawn gradually from the Park to allow native bees to increase and pollinate these orchard crops.