Pollination Potential of the Bee Osmia aglaia for Cultivated Red Raspberries and Blackberries (Rubus: Rosaceae)

Abstract

A manageable cavity-nesting bee, Osmia aglaia Sandhouse (Apiformes: Megachilidae), was evaluated as a pollinator for cultivated red raspberry and blackberries. Floral visits by free-flying honey bees or by less numerous caged O. aglaia yielded red raspberry fruit (`Canby' and `K81-6') of equivalent size. These fruit were 30% larger (1.9 g, 70 drupelets) than fruit from unvisited flowers. Female O. aglaia readily visited flowers of all eight diverse blackberry cultivars observed. For all of these cultivated Rubus, female O. aglaia were observed to invariably collect pollen while pivoting atop the brush of pistils, maximizing opportunities for pollen transfer. Within its native geographic range in western Oregon and California, this effective native pollinator could be a sustainably managed, economical bee for cultivated cane fruit.