Examination of hivetop incubator efficacy for emerging Osmia lignaria (Hymenoptera: Megachilidae) and the impact on Apis mellifera (Hymenoptera: Apidae) colonies

Authors: McCabe, Lindsie; Cox-Foster, Diana; Pitts Singer, Theresa

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2022
Publication Date: 1/28/2023
Citation: McCabe, L.M., Cox-Foster, D.L., Pitts-Singer, T. 2023. Examination of hivetop incubator efficacy for emerging Osmia lignaria (Hymenoptera: Megachilidae) and the impact on Apis mellifera (Hymenoptera: Apidae) colonies. Journal of Economic Entomology. 116(2):359-367. https://doi.org/10.1093/jee/toad002.
DOI: https://doi.org/10.1093/jee/toad002

Interpretive Summary: The blue orchard bee (BOB) is an important pollinator for U.S. agricultural crops, especially early spring orchard crops when combination with honey bees. BOBs usually requires artificial warming to synchronize bee emergence with crop bloom. The Hive Top Incubator (HTI) was invented to create a heated space atop Honey bee colony for incubation of BOBs and to minimize the labor needed for releasing bees for pollination. Here we examine the use of HTIs for warming and releasing BOBs under Utah and Washington spring conditions. We found no differences between the internal temperatures of the honey bee colonies with or without HTI; all internal hive temperatures were maintained at a relatively constant temperature of approximately 33° C. For the honey bee colonies, presence of the HTI did not have a significant impact on the brood production or colony growth. BOBs emerged 3× faster when placed in an HTI atop a honey bee colony. The number and distribution of BOB nests was not correlated to the location of HTIs, indicating that the BOBs were able to distribute themselves after emergence. Overall, HTIs were demonstrated to be an important tool for releasing BOBs for pollination with no evidence of negative impact on honey bee colonies.

Technical Abstract: Osmia lignaria (the blue orchard bee; Hymenoptera: Megachilidae) is an important pollinator for U.S. agricultural crops, especially early spring orchard crops in combination with honey bees. The deployment of O. lignaria usually requires artificial warming to synchronize bee emergence with crop bloom. The Hive Top Incubator (HTI) was invented to create a heated space atop a Apis mellifera L. (Hymenoptera: Apidae) colony for incubation of O. lignaria and to minimize the labor needed for releasing bees for pollination. In the HTI, diapausing O. lignaria adults in cocoons can be incubated to break diapause, chew out of cocoons, and fly out to the orchards to make nests in provided nesting sites and thereby pollinate a crop. Here we examine the use of HTIs for warming and releasing O. lignaria under Utah and Washington spring conditions. We address three main objectives: 1) determine if the presence of HTIs inhibit the ability of A. mellifera colonies to adequately thermoregulate or cause negative impacts on colony growth, 2) compare the duration of O. lignaria adult emergence from an HTI with and without the heat provided by an honey bee colony, and 3) assess the dispersal and nesting success of HTI-emerged O. lignaria from honey bee colonies at the edge of an orchard to nesting sites distributed throughout the orchard. We found no significant differences between the internal temperatures of the A. mellifera colonies with and without HTI; all internal hive temperatures were maintained at a relatively constant temperature of approximately 33° C. For the honey bee colonies, presence of the HTI did not have a significant impact on the brood production or colony growth. Osmia lignaria emerged 3× faster when placed in an HTI atop a honey bee colony. The interior temperatures of HTIs were significantly less than the temperatures of the honey bee colonies, but significantly warmer than interior temperatures of HTIs atop empty hive boxes. The number and distribution of O. lignaria nests was not correlated to the location of HTIs at the edge of a field, indicating that the O. lignaria were able to distribute themselves after emergence. Overall, HTIs were demonstrated to be an important tool for releasing O. lignaria for pollination with no evidence of negative impact on A. mellifera colonies.