A COMPARISON OF THE ALFALFA LEAFCUTTING BEE (Megachile rotundata) AND THE HONEY BEE (Apis mellifera) AS POLLINATORS FOR HYBRID CARROT SEED IN FIELD CAGES

摘要

The alfalfa leafcutting bee (ALB) is the pollinator of choice for alfalfa in western North America. Because of its preference for legumes, it has long been overlooked as a potential pollinator of other openfield crops: It is presently unclear what crops the ALB might pollinate in cages. I compared the pollination efficiency of the ALB with that of the honey bee (HB) on hybrid carrots using a male steril 'Imperator' line and a 'Nantes' male fertile line in field cages in Idaho. Three cages each contained a standard deep super of honey bees (c. 3000 aduts with four frames of brood); three other cages received approximately 100 male and 50 female ALBs. The honey bees were also supplied with corn syrup, a protein patty and water. The ALB cages were furnished with non-blooming alfalfa plants for leaf cuttings, and ALB nest blocks. For the 'Imperator' line, there was no significant difference in seed production between HB or ALB treatments (2228 and 2158 mg seed/primary inflorescence; ANOV, P> 0.25), nor was there a difference in the percent seed germination between the pollination treatments (ANOV, P> 0.20). ALB brood reared on carrot pollen and nectar reached adult weights indistinguishable from that of brood reared on alfalfa. For the pollination of hybrid carrots, 30 female ALBs seem equivalent to 100 times as many worker honey bees.