Sonication—also known as buzz pollination—is a method that some bees use to release pollen from stubborn flowers. Plants such as tomato, potato, blueberry, and cranberry have flowers that do not easily release their pollen. Bees capable of sonication grab onto these flowers and vibrate their flight muscles (without moving their wings) until the pollen is shattered loose. Once the pollen is freed the bees groom it from their bodies and pack into pollen sacks for the trip back to the nest.
The most famous sonicating bee is the bumble bee, but there are also a few solitary bees that do it as well, such as Australia’s blue-banded bee. Tomatoes grown in greenhouses (where there is no wind) are completely dependent on bumble bees to set fruit. Honey bees are incapable of sonication and so are useless for those crops that absolutely require it.
Crops such as blueberry and cranberry can be pollinated by either honey bees or bumble bees, but bumble bees are much more efficient because of their use of sonication. If honey bees are used to pollinate those crops, vast numbers of foragers are required to get the job done.