Blueberries

Blueberries, huckleberries and their relatives belong to the genus Vaccinium in the heath family (Ericaceae). Among the kinds sought for their edible berries, both the wild species and their cultivated derivatives require bee visitation to their flowers for fruit production. Pollen is shed through a pair of pores at the tip of each anther. Like a salt shaker, a bee can remove more pollen removal from these anthers by vibration. Bumblebees and a number of diverse nonsocial native bees in both North America and Europe are effective pollinators of various blueberries; honey bees can be effective pollinators of highbush blueberry if the weather is warm during bloom.

Pollination

Blueberries, huckleberries and their relatives belong to the genus Vaccinium in the heath family (Ericaceae). Blueberries are unusual among cultivated fruits, in that cultivars and varieties may be the result of intentional crosses between two or more species. Furthermore, although the taller, more shrubby varieties are typically planted as rows of rooted cuttings from a single parent plant (and thus are genetically identical), so-called "lowbush" blueberries are typically produced on naturally occurring "barrens" where production has been favored through use of fertilizers, burning, and removal of competing vegetation.

Among the kinds sought for their edible berries, both the wild species and their cultivated derivatives require bee visitation to their flowers for fruit production. Flowers of species in the temperate zone are typically white, nodding and urn-shaped to cylindrical. The dimensions of the flowers, especially the depth of the corolla and the breadth of its opening, often defines which bee species can easily reach the nectaries and consistently contact the stigma while foraging. All visitors take nectar from the basal nectaries if they can be reached. Pollen is shed through a pair of pores at the tip of each anther. Like a salt shaker, a bee can remove more pollen removal from these anthers by vibration, either by buzzing their flight muscles or else drumming the anthers using their legs. Little pollen is removed by bees that simply probe the flowers for nectar. Some species steal nectar through holes that they make (or find) cut in the side of the flower's corolla; these individuals fail to contact the flower's stigma and so transfer no pollen.

A southern highbush blueberry developed for the Gulf region of the U.S.

Northern highbush blueberry is largely self-compatible, which is why planted blocks of a single variety can be used for commercial fruit production. There is evidence that cross-pollination with another variety can enhance its fruit production. Many varieties of rabbiteye blueberry are self-incompatible; pollen must come from another variety to effectively fertilize its ovules and yield a berry. Two or more compatible varieties must be planted together (often in neighboring rows) for commercial fruit production. Likewise, lowbush blueberries are self-incompatible. Here, effective pollen must come from neighboring clones in the semi-managed barrens.

Pollinators

Bumblebees and a number of diverse nonsocial native bees in both North America and Europe are effective pollinators of various blueberries. Honey bees can satisfactorily pollinate the some self-fertile species, such as commercial clones of highbush blueberry. Our earlier studies showed that bumblebee queens and the ground-nesting solitary bee Habropoda laboriosa (southeastern blueberry bee) are responsible for much of the fruit production of rabbiteye blueberry in the southeastern US. Alfalfa leafcutting bees have also been used for blueberry pollination in Canada. At our lab, the cavity-nester Osmia ribifloriscontinues to be studied for commercial blueberry pollination. It currently presents several difficulties:

1. inconsistent availability of wild populations for starting managed populations
2. tendency to disperse from nesting sites
3. native distribution restricted to drier parts of the western U.S.

Osmia ribifloris, a blueberry pollinator	Bumble Bee Queen (Bombus vosnesenskii)

If starting populations can be obtained, another Osmia species will be studied with Kenna MacKenzie and Steve Javorek at the AgCanada Research Centre in Kentville, Nova Scotia. This cavity-nesting species is more widely distributed in regions where blueberries are grown commercially.