Native bee and honey bee foraging in Oregon cranberry

Pollination is critical in cranberries for good fruit size, conformation and yield. Honey bees, Apis mellifera, are presently used to service cranberries, but their performance may be limited due to their tendency not to forage during adverse weather and lack of loyalty to the crop. The objective of this study was to examine native bee fauna and compare foraging by native bees and honey bees in cranberries. Blue vane traps were used to estimate native bee diversity and abundance in four cranberry farms on the southern Oregon coast. At the site with the harshest weather, two minute counts were taken; temperature and wind speed were noted along with any bees foraging on bloom. At the same site, honey bees and bumble bees were captured and their pollen loads removed for composition analysis. Of over five-hundred bees trapped during cranberry bloom in 2008; 4 families, 13 genera and over 26 species were represented. The genera that were most abundant were: Agapostemon (35%), Bombus (15%), Evylaeus (14%), and Synhalonia (10%). While 5 Bombus species were collected, the two closely related species B. vosnesenskii and B. caliginosus comprised >70% of the bumble bees. The two-minute count data revealed a strong correlation between high wind speed and foraging by Bombus but not by A. mellifera. The pollen data has yet to be analyzed. Implications of this study will be discussed.