Flowers can infect visiting bees with parasites that are known to cause lethargy, dysentery, colony collapse and queen death in heavily infected bees, a new study has found.
"Flowers are hotspots for parasite spread between and within pollinator populations," said Peter Graystock, a postdoctoral researcher in the Department of Entomology at the University of California, Riverside and a member of the research team.
"Both the flower and bee species play a role in how likely parasite dispersal will occur," he said.
The study is the first to show that not only can bees disperse parasites around the environment but also that flowers are platforms for a host of pollinator parasites subsequently dispersed onto visiting bees.
"By showing that visits from parasite-carrying bees can turn flowers into parasite platforms, we can say that it is likely that heavily visited flowers may become more 'dirty' with bee parasites," said Graystock.
"Planting more flowers would provide bees with more options, and parasite spread may thus be reduced," he said.
The researchers found four common honey bee and bumblebee parasites to be dispersed via flowers - Nosema apis (causes a honey bee disease), Nosema ceranae (causes an emergent disease in honey bees and bumblebees), Crithidia bombi (causes a bumblebee disease) and Apicystis bombi (mostly found in bumblebees).
These parasites are known to cause, lethargy, dysentery, colony collapse, and queen death in heavily infected bees.
Currently, bees are frequently transported across state and international territories. Quarantine and parasite screening usually cover only the screening of host-specific diseases.
But bumblebees can transport honey bee parasites, and vice versa, the research team has now shown, and proposes that increased screening protocols be employed to protect pollinator diversity.
"Our finding may also affect the national and international trade of flowers unless sterilisation of parasites on these flowers can be guaranteed," said Graystock.
"Otherwise flower movements may also be moving pollinator parasites to new territories," he said.
In their experiments, Graystock and his colleagues allowed one species of bee (honey bees or bumblebees) from hives containing parasites to forage on flowers for three hours.
The bees were then removed and a second group of flowers were added to the foraging arena along with colonies of a second bee species (a species not used before).
The new bees then foraged upon the new and previously foraged flowers for three hours.
All flowers were then sampled. Parasites found in the original patch confirmed parasite dispersal by the original hosts. Parasites found in the new group of flowers confirmed the non-target bee was able to disperse the parasites.
The study was published in the Proceedings of the Royal Society B.
