If you’re a home gardener, it’s unlikely that you’ll be renting hives of honey bees to pollinate your few blueberry plants, as commercial blueberry growers do.
So in a way, the information provided here about blueberry pollinating insects is just an interesting side note.
But it might be fun to watch your blueberry plants while they’re in bloom just to see which insects are working the hardest at helping you produce a great crop of blueberries.
There are a number of insects that are minor blueberry pollinators, and those vary some from region to region. But in general, the two primary blueberry pollinators are bumblebees (a catchall term that refers to a number of Bombus species) and honey bees.
Bumblebees are the most effective at blueberry pollination. Their tongues are long enough to reach through the long, narrow blueberry blossom to the base where the nectar is secreted. Honey bees have shorter tongues, and have more difficulty reaching the nectar.
Bumblebees also use a unique method of collecting pollen, called ‘sonication,’ which makes it a more effective pollinator.
When a bumblebee collects pollen from a blossom, it will hang upside down on the flower, with the opening of the flower positioned over the bees’ belly. It then vibrates its flight muscles, dislodging grains of pollen that fall from the flower onto the bees’ belly. The bee then brushes the pollen grains from its belly into the pollen baskets on its hind legs.
If you gently hold a twig between your fingers that’s attached to a blossom that a bumblebee is sonicating, you’ll easily be able to feel the vibrations of the bee at work. It’ll feel as if the twig is buzzing in your fingers.
Sonication is extremely effective at pollinating a self-fertile flower, but it’s not effective for cross-pollinating. Bumblebees cross-pollinate as they go from flower to flower gathering nectar.
If you just compare a single bumblebee to a single honey bee to decide which is the most effective at blueberry pollination, it wouldn't even be close.
The bumblebee would win the contest hands down.
But honey bees hold one singular advantage over bumblebees that makes them the #1 pollinator of commercially grown blueberries – numbers. A single hive of honey bees can number in the tens of thousands in population.
So while a single honey bee can’t do the pollinating work of a bumblebee, hundreds or even thousands of honey bees certainly can.
That’s why many commercial blueberry growers pay beekeepers to temporarily scatter hives of honey bees throughout their blueberry orchards. It’s worth the expense, because the busy guest workers can significantly increase the quantity and quality of the harvest.
Another type of bee that can often be found buzzing amongst the blueberry blossoms is called the carpenter bee.
Carpenter bees are small, and have no hope of reaching through the open end of the blossom to the nectar at the base of the flower. Their tongues simply aren’t long enough to reach that tantalizing pool of nectar at the bottom of the blossom.
But that doesn’t mean that the carpenter bees are left out; they still manage to snag their share of the sugary treasure. They take a shortcut by snipping out a small incision at the base of the flower. It’s then an easy reach for them through the hole and right to the nectar.
That solves the problem as far as the carpenter bee is concerned, but itcreates a problem for you, the blueberry grower.
That’s because the carpenter bees’ shortcut allows it to completely bypass the pollen-bearing parts of the flower. So as the carpenter bees gather nectar, they do no pollinating at all. They sort of cheat the blueberry plant, you might say – treasure taken without services rendered.
But what’s worse is that honey bees that come along later and visit the same blossom will take advantage of the carpenter bees’ shortcut and slurp nectar through the hole – again without doing a bit of pollinating.
So if an area has a high population of carpenter bees, the effectiveness of honey bees as blueberry pollinators is diminished. (Interestingly, bumblebees just ignore the carpenter bees’ shortcuts, and always probe for nectar from the top of the flower. No cheating for the bumblebee!).
Fortunately, though, not all honey bees take advantage of the carpenter bees’ shortcut.
I’ve spent many hours watching the bees at work in our blueberry orchard. (I guess you could say I’m easily entertained!). And I’ve noticed that some honey bees ALWAYS use the carpenter bee hole, and some honey bees ALWAYS probe for nectar from the top, whether the blossom has a carpenter bee hole in it or not.
So carpenter bees don’t eliminate the effectiveness of honey bees as blueberry pollinators, they just diminish it somewhat.