Native bee diversity and pollen foraging specificity in cultivated highbush blueberry (Ericaceae: Vaccinium corymbosum L.) plantings in Rhode Island

We identified 41 species of native bees from a total of 1083 specimens collected at cultivated highbush blueberry plantings throughout Rhode Island in 2014 and 2015. Andrena spp., Bombus spp. and Xylocopa virginica (L.) were collected most often. Bombus griseocollis (DeGeer), B. impatiens Cresson, B. bimaculatus Cresson, B. perplexus Cresson, and Andrena vicina Smith collected the largest mean numbers of blueberry pollen tetrads. The largest mean percent blueberry pollen loads were carried by the miner bees Andrena bradleyi Viereck (91%), A. carolina Viereck (90%), and Colletes validus Cresson (87%). The largest mean total pollen grain loads were carried by B. griseocollis (549,844), B. impatiens (389,558), X. virginica (233,500), and B. bimaculatus (193,132). Xylocopa virginica was the fourth and fifth most commonly collected bee species in 2014 and 2015 respectively. They exhibit nectar robbing and females carried relatively low blueberry pollen loads (mean 33%). Overall we found 10 species of bees to be the primary pollinators of blueberry in Rhode Island. Most bee species nest underground. Andrena spp. are known to typically prefer sandy soils near forest edges or openings, but individual species data tends to focus on the biology and behavior of the bee and not soil characteristics. We discovered nests of Andrena crataegi Robertson underneath apple trees while collecting bees from commercial and research highbush blueberry plantings in Rhode Island. We identified the soil texture, percent organic matter, bulk density, and pH of the soil at the nest site. Depending on depth, the soil was found to be either or silt loam or silt, percent organic matter ranged from 2.6–8.4%, bulk density ranged from 1.0–1.5 g/cm3, and pH ranged from 4.8–5.0. Further study is required to better understand the nesting requirements of this bee, with consideration of how site specific characteristics influence the agriculturally significant bee species in an area