Date of Award

12-2013

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Advisor

Francis A. Drummond

Second Committee Member

David E. Yarborough

Third Committee Member

Eleanor Groden

Abstract

The lowbush blueberry (Ericaceae: Vaccinium angustifolium) is native to North America. Insect pollination is required for fruit set and bees (Hymenoptera: Apoidea) are the most common and efficient pollinators. Growers rely on combinations of managed honeybees, commercially reared bumblebees and naturally occurring wild bees for pollination services.

This study explores three main questions important for understanding wild bee communities associated with lowbush blueberry production. 1. What is the diversity and abundance of wild bees in Downeast Maine blueberry fields and what factors impact the bee communities? 2. Does the use of commercial bumblebees (Bombus impatiens Cresson) impact wild bumblebee communities by contributing to the prevalence of the microsporidian parasite Nosema bombi? 3. What economic contributions do wild bee communities provide to blueberry growers?

This study documents 133 wild bee species found in 40 study fields, along with an additional six species from supplemental fields. Twenty-two of these species have not been previously recorded in Maine. Wild bee diversity fluctuates over the three study years with no evidence that farm management practices influence bee community structure. Wild bee abundance is negatively related to the proportion of blueberry cropland within 500 m of the field borders and positively related to the proportion of deciduous forest and cleared forest within 500 m.

Based on a sample of 767 bumblebee workers caught over a two-year period, Nosema infection levels of 5.48% were recorded. Infection levels have no relation to the use of commercial Bombus impatiens colonies for pollination, providing no support for a pathogen spillover hypothesis. Populations of B. terricola (Kirby) show evidence of decline with a Nosema infection prevalence of 46.2%, a local trend which reflects nationwide patterns.

Three fruit set measures, yield (kg/ha), and value of crop (dollars/ha) were recorded for the study fields. Fruit set, yield, and value of crop were positively related. Fruit set, yield, and value of crop were also positively related to the abundance of all wild bees, bumblebees, and honeybees recorded foraging in the fields. Wild bee and bumblebee activity influenced fruit set and yield measures with 2-8 times the impact of honeybees.

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