"Wild and managed bees are in decline at national and global scales," biologist Mathias Fuerst of Royal Holloway University of London said. "Given their central role in pollinating wildflowers and crops, it is essential that we understand what lies behind these declines."
Two common honeybee diseases -- deformed wing virus and the fungal parasite Nosema ceranae -- have been found to be infecting wild worker bumblebees, the researchers reported in the journal Nature.
"Our results suggest that emerging diseases, spread from managed bees, may be an important cause of wild bee decline," Furst said.
The findings suggest it is vital for beekeepers across the world to ensure honeybee management supports wild bee populations, the researchers said.
"National societies and agencies, both in the United Kingdom and globally, currently manage so-called honeybee diseases on the basis that they are a threat only to honeybees," Royal Holloway scientist Mark Brown said.
"While they are doing great work, our research shows that this premise is not true, and that the picture is much more complex," he said. "Policies to manage these diseases need to take into account threats to wild pollinators and be designed to reduce the impact of these diseases not just on managed honeybees, but on our wild bumblebees too."