ARS | Publication request: A COMPARISON OF THE ALFALFA LEAFCUTTING BEE (MEGACHILE ROTUNDATA) AND THE HONEY BEE (APIS MELLIFERA) AS POLLINATORS OF HYBRID CARROTS IN FIELD CAGES.

Submitted to: Journal Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 1997
Publication Date: N/A

Interpretive Summary: Hybrid carrot seed is produced commercially by growing male-sterile and male-fertile varieties in field cages. To move pollen between the varieties, insect pollinators, usually honey bees, are used. Growers have become increasingly displeased with using honey bees as pollinators in field cages, however, because honey bees become irritable and difficult to deal with when confined. A more docile and easily managed species, the alfalfa leafcutting bee, has the disadvantage of preferring to visit flowers of plants in the legume family when available. However, it is not known if this species will pollinate carrot flowers when confined in cages with them. I compared the pollination efficiency of the alfalfa leafcutting bee with that of the honey bee by estimating seed yield and seed germination rates. There was no difference in either variable between bee species. In addition, alfalfa leafcutting bees produced healthy, normal-sized progeny using carrot pollen and nectar. Indeed, there were no differences in size between progeny reared on carrots and progeny reared on alfalfa. Thus, about 30 alfalfa leafcutting bee females are as efficient at pollinating carrots as 100 times as many honey bees.

Technical Abstract: 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 ignored as a potential pollinator of other open field 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 sterile'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 adults 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. There was no significant difference between HB or ALB visited inflorescences in seed production by the 'Imperator' line e(ANOV,P > 0.25), nor was there a difference in the percent seed germinatio between the pollination treatments (ANOV,P > 0.20). ALB brood reared on indistinguishable from that of brood reared on alfalfa. For the poll- ination of hybrid carrots, 30 female ALBs seem equivalent to 100 times as many worker honey bees.