The diversity and importance of wild bees as pollinators in apple orchards

Background/Question/Methods

There is an increasingly large gap between the pollination services provided by honeybees and the demand for insect dependent crops. This gap is filled by wild and native pollinators that provide free pollination services without being managed.  The true extent of these unmanaged pollination services, however, remains unknown. Our objective was to quantify the importance of communities of wild bees in apple orchards, an insect dependent and economically valuable crop.

We collected bees in 28 apple orchards across the Fingerlakes region of western New York from 2008-2013. Our survey included more than 760 sampling events and comprised more than 160 sampling hours. From the scopa and bodies of ten individual bees of each of 14 species representing different bee functional groups, we counted and identified pollen grains. We use the proportion of apple pollen carried by each bee as a proxy for effectiveness, and calculate pollinator importance as the effectiveness multiplied by the average abundance of bees in each orchard.

Results/Conclusions

Wild bees are diverse, abundant, and important pollinators in apple orchards. We collected more than 11,000 bee specimens, representing 104 species from five different bee families. Though the family Halictidae was represented by the greatest number of bee species, bees of the genus Andrena alone comprised 42% of all bee abundance. Bees of this genus also carried a very high proportion of apple pollen, with fewer contaminants, than other bee genera. Given these facts, bees of the genus Andrena were found to be more important than the honeybee in many orchards, even in some orchards where honeybee hives had been rented for pollination. We demonstrate that these wild bees can be equal or greater in importance than the honeybee despite the lack of management. This suggests that, for many apple orchards, renting honeybee hives is an unnecessary expense.