HONEYBEES have been busy – spreading diseases to insects that pollinate crops. It seems imported honeybees are an important reservoir for viruses that kill wild pollinators, which could lead to a meltdown in the planet's pollination services.
World trade in honeybee colonies contributes to honey production and also plays a vital role in agriculture – in some cases there would be no crop without the pollinators.
Honeybee colonies in Europe and North America have suffered recent mysterious declines. But now it seems the colonies could be just as much of a threat to wild pollinators such as bumblebees and the many species of "solitary" bees.
Matthias Fürst of Royal Holloway, University of London tracked the geographical prevalence in the UK of a non-native parasite called deformed wing virus (DWV) that is often found in both honeybees and bumblebees. The virus is spread by a mite and typically kills bees within 48 hours. The pattern of spread showed that imported honeybees are the major source of infection for the wild pollinators, and that emerging diseases spread by those colonies could be a major cause of mortality in the wild (Nature, DOI: 10.1038/nature12977).
"This is a previously unrecognised threat," says Fürst. While his study looked mainly at how diseases move from honeybees to bumblebees, he warned that the problem "may well play a particularly significant role for already rare and vulnerable pollinator species". The UK alone is home to around 250 different species of wild solitary bees.
Previous studies in the US have found that honeybees carry a range of viruses, including DWV, Israeli acute paralysis virus, black queen cell virus and sacbrood virus, all of which may be passed on to other pollinators.
Disease spread by honeybees is one more in a growing list of threats to wild pollinators, says Matt Shardlow, head of UK NGO Buglife. "Pollinators are suffering declines as a result of several linked factors including habitat loss, pesticides and disease." But, he says, "this study adds to a developing picture that diseases are a major risk to wild pollinators, and strongly suggests that imported honeybees are the main reservoir for diseases".
Trade in honeybees is controlled by the World Organisation for Animal Health, which has rules to promote free trade while restricting the spread of diseases. But Shardlow says governments must introduce strict hygiene regulations to protect wild pollinators, worth an estimated £500 million a year to the UK economy alone.
Fürst says there is no immediate threat to individual crops, since most are pollinated by a variety of insects. "But to keep it that way we need to protect our bees and keep populations healthy and diverse."
This article appeared in print under the headline "Honeybee trade is hotbed for disease"
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