A novel pollen transfer mechanism by honey bee foragers on highbush blueberry (Ericales: Ericaceae)

Honey bees (Apis mellifera L. (Hymenoptera: Apidae)) are effective pollinators of many crops but are thought to be inefficient in pollinating blueberries (Vaccinium corymbosum L.) due to their inability to buzz pollinate. Nonetheless, commercial growers rent honey bee hives for pollination, resulting in the dominance of honey bee workers visiting flowers during bloom.The objective of this study was to examine where on the honey bee pollen is carried and how it is transferred from flower to bee to the stigma of other flowers. Examination of 90 honey bee workers foraging on blueberry flowers documented that blueberry pollen tetrads were present on all body parts. Relative amounts were as follows: head 12%, body 6%, legs 19%, and tarsi 63%. Quantities on the body subregions ranged from an average of 400 tetrads on the basitarsi to 16 on the fore tarsal claws. Thus, a single contact between many of the pollen-carrying body parts and a stigma has the potential to transfer significant amounts of pollen. The study also revealed that bee behaviors unrelated to the intentional collection of nectar and pollen, such as the frequent touching of stigmas by the claws, tarsi, or legs, while foraging, grooming, and walking across flower clusters, could result in pollen transfer. These contacts occurred 65.9% of the time a honey bee landed on a flower cluster. These findings have broad implications for future assessments of the efficiencies of various bee species in pollinating diverse crops and plants.