Two diseases of honeybees are spreading to wild bumblebees, Royal Holloway University of London researchers have found.
Wild insects infected with deformed wing virus (DWV) and the single-cell parasite Nosema ceranae were present across England, Scotland and Wales, they found. The decline of the UK's bumblebees over recent decades has been attributed to habitat loss, but this latest finding suggests an additional factor.
Professor Mark Brown from Royal Holloway, University of London said: "These pathogens are capable of infecting adult bumblebees and they seem to have quite significant impacts."
In honeybees, the effect of DWV is exacerbated by the presence of another widespread parasite, the varroa mite, which bumblebees do not carry. Despite this, the new research shows that bumblebees infected with DWV had "a significantly shorter lifespan", Brown pointed out.
Having surveyed 26 sites, the researchers found that approximately 11 per cent of the bumblebees were infected with DWV and seven per cent with N. ceranae, compared with 35 per cent and nine per cent respectively of honeybees.
"They are sharing parasite strains," Brown explained, and urged: "At national and international levels, we have to enable our beekeepers to keep their bees as free of diseases as possible. The benefits are not just to the honeybees, they are to the wild bees as well."
Brown added that any additional effect of neonicotinoid pesticides on infected bees "is something we are hoping to test later".
Australia's honeybee population has not declined since the introduction of neonicotinoid pesticides in the mid 1990s, a report from the Australian Pesticides & Veterinary Medicines Authority has concluded. It stated: "The introduction of neonicotinoids has led to an overall reduction in the risks to the agricultural environment from the application of insecticides."