Viruses that could play a role in the recent decline in honeybee colonies may be spreading through flower pollen, new research finds. What's more, a number of wild pollinators, such as bumblebees, yellowjackets, and wasps, can also become infected with viruses in the pollen.

In hives affected by colony collapse disorder—a phenomenon that surfaced in U.S. honeybee colonies in 2006—worker bees vanish en masse. Some studies have suggested that Israeli acute paralysis virus (IAPV), first identified in 2002, may be contributing to the bees' demise.

Scientists knew that several viruses that infect honeybee colonies are transmitted from one bee to another within the hive through the bugs' saliva or from an infected queen to her eggs. But how the viruses moved from hive to hive was relatively unknown, said study leader Diana Cox-Foster, an entomologist at Pennsylvania State University. "People suspected the viruses were being transmitted by bees visiting other colonies, but no one really knew there was evidence for the virus moving into other [insect] species," she said.

Bees collect nectar to make into honey and to make "bee bread"—pollen packed by workers into tiny balls with a bit of nectar added. When Cox-Foster's team collected university-owned honeybees as the insects were harvesting pollen, they found that some bees were healthy but their pollen loads were contaminated. This indicated that at least one type of virus—deformed wing virus, another fatal bee disease—was spreading from the pollen to the bees, and not always the other way around.

In a separate experiment, the team collected and examined wild bumblebees and wasps and discovered molecular evidence of viruses that can infect honeybees. When bees from a healthy hive visited the same flowers previously visited by sick bumblebees, the colony contracted the virus within a week, the team found.