The Bluecrop variety of blueberry presents unique challenges in setting fruit. In a year when there are few bees it is not uncommon to see bees drawing nectar for the base of a flower that has become separated from the base. This, of course, subverts the whole process of pollination. In a year like this year, when there are lots of bees, foraging without pollinating is never seen. A plausible explanation is the following:
Dr. Gary C. Pavlis
County Agricultural Agent
Pollination: Unfortunately not all of the visitations to blueberry flowers by bees result in pollination. Pollen must be transferred from some parts of the bee’s body, usually the head to the tip of the pistil (stigma) in order to achieve pollination. There are three ways in which honeybees “cheat” the grower by not earning their rental fee. 1) Acquire nectar by feeding through hole in blossom made by a carpenter bee. 2) The distance from the edge of a flower petal to pistil is very wide, as in Earliblue. The bee can stick its tongue down and get the nectar without touching the pistil. 3)The bee does not thrust through the open end but gets nectar through the bottom – very important in Bluecrop and Jersey. In some years such a high percentage of the bees may work through the bottom of the corolla that the crop can be significantly reduced. Bees develop this bad habit mostly on Jerseys and Bluecrop. The probable reason is that both of these varieties can produce small seedless berries without pollination (parthenocarpy). These parthenocarpy berries begin to develop shortly after the flowers open and once it starts the corolla becomes loose at the base after a few days, enabling the bee to secure its nectar through the loose juncture of the corolla and ovary. Since the honeybees usually select older flowers which have more nectar it enables the younger ones to start the parthenocarpic process which does not occur once the flower is pollinated. The solution may be to use higher concentrations of bee hives.
The higher numbers of bees per bush forces them to accept younger flowers with the result that more berries are developed from bee pollination than by parthenocarpy.
Source: http://njaes.rutgers.edu/pubs/blueberrybulletin/2009/bb-v25n06.pdf
