An assessment of artificial nests for cavity-nesting bees (Hymenoptera: Megachilidae) in lowbush blueberry (Ericaceae)

Fluctuating bee (Hymenoptera: Apoidea) populations jeopardise pollination services. Nesting habitat for solitary bees is potentially limited in many agroecosystems, but the provision of artificial nests could augment bee communities and the pollination services they provide. We investigated whether cavity-nesting bees (Hymenoptera: Megachilidae) in lowbush blueberry (Vaccinium angustifolium Aiton (Ericaceae)) fields would use artificial trap nests. Different nest designs were compared, as was nesting occupancy between fruit-bearing and vegetative fields. Milk carton nests had significantly more uptake by and emergence of Osmia Panzer and Megachile Latreille than wooden nests. Only 3% of wooden nests had at least one occupied nesting tube versus 73% of milk carton nests, with a total of 34% nesting tubes occupied. Bee emergence was significantly higher in nesting tubes from fruit-bearing fields than vegetative fields. Osmia and Megachile emergence was low from milk carton nests, with bees emerging from less than 10% of occupied nesting tubes, in large part due to parasitism. Overturned clay lids were tested as potential nesting sites for Osmia inermis Zetterstedt, but only 3% of lids had nesting evidence. Our results suggest that certain artificial nests have potential for encouraging communities of cavity-nesting bees, but further study on nest design and handling protocols is needed.