Willows (Salix spp.) as pollen and nectar sources for sustaining fruit and berry pollinating insects.

Ostaff, D.P., Mosseler, A., Johns, R.C., Javorek, S.K., Klymko, J., and Ascher, J.S. (2015). "Willows (Salix spp.) as pollen and nectar sources for sustaining fruit and berry pollinating insects.", Canadian Journal of Plant Science, 95(3), pp. 505-516. doi : 10.4141/CJPS-2014-339  Access to full text


Willows (Salix spp.) are ubiquitous in the northern hemisphere, serving as an important pollen and nectar resource for insect pollinators and for the enhancement of insect-pollinated agricultural crops such as fruits and berries. We used a common-garden field test containing seven native North American willow species to assess attractiveness of male and female flower catkins by documenting visits of Andrena spp. (Apoidea: Anthophila), other wild bees (all native), and flower flies (Syrphidae). Most willows in Canada's Maritimes begin flowering very early in spring, as the first wild pollinators become active following winter, and stop flowering by mid-May. A later-flowering group normally begins flowering in mid-May and stops flowering by mid-June. Pollinator species were largely opportunistic, visiting whatever species of willow flowers were available during foraging, but Andrena dunningi appeared to prefer flowers of S. nigra and S. interior. There was a general preference for male flower catkins, with 72% of Andrena spp. and 82% of all flower flies collecting pollen and/or nectar from male flowers, because pollen is the major component of nest provisioning for most solitary bees and the major source of protein used to develop reproductive tissues in most flower flies. Most andrenids and flower flies were collected within the April–June flowering period of six of the seven willow species studied, indicating that these willows could be used to support the pollinator community before the flowering period of commercially valuable flower-pollinated crops such as lowbush blueberry, cranberry, and apple.

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