By Richard Gray, Science Correspondent
Bumblebees imported from abroad to pollinate fruit crops and garden flowers are spreading disease among native insects and may be driving the widespread decline of bees.
An estimated 40,000 to 50,000 colonies of bumblebees are imported to England each year to help pollinate crops such as strawberries and tomatoes.
The commercially bred bumblebees are also now being sold to gardeners for around £100 a hive to them help pollinate flowers in their gardens.
Researchers found that 77 per cent of colonies they tested as they arrived in Britain carried parasites.
The colonies were found to be carrying five parasites that can infect bumblebees and five parasites that infect honeybees.
The scientists behind the project claim the imported bees can increase the prevalence of disease in Britain by infecting native bees and could also bring new diseases with them.
Bumblebees have suffered dramatic declines in recent decades, with their numbers falling by more than 60% since the 1970s and two species becoming extinct.
Honeybees have also seen their numbers half in the past 25 years.
New diseases such as the varroa mite along with harm caused by pesticides and habitat loss are thought to have placed excessive pressure on bee colonies.
Professor William Hughes, a biologist at the University of Sussex and one of the authors of the new study, said: “Around a million colonies are exported globally every year from a small number of factories in central and Eastern Europe.
“The bees are supposed to be disease free when they are exported under license requirements, but we have shown that this is not the case.
“The amount of disease they are carrying is huge. We found honeybee parasites as well as bumblebee parasites.
“The parasties we found are similar to those already found in the UK, but they could easily bring in a new diseases as happened in Argentina recently.
“They could also be brining more virulent forms of the parasites with them and are certainly increasing the presence of the parasites in the areas where the bees are released.”
Professor Hughes and his colleagues, whose findings are published in the Journal of Applied Ecology have now called on Natural England, which licenses the import of bumblebees, to make more stringent checks to ensure bees are disease free.
They are also appealing to the bumblebee suppliers to make more effort to eradicate disease in the colonies they export.
Honeybees are commonly used by farmers to help pollinate crops and many honeybee keepers often hire out their hives to do this each year.
Some crops, such as tomatoes and strawberries, rely upon bumblebees to pollinate them.
However, there are few bumblebee colonies produced commercially in Britain and instead they are bred in factories in countries like Slovakia.
These are then flown in aircraft around the world to be used in greenhouses and polytunnels to pollinate fruit crops.
Recently, hives of bumblebees are now being sold to gardeners for use in domestic gardens.
Professor Hughes and Dr Peter Graystock of the University of Leeds found three major bumblebee parasites – Crithidia bombi, Nosema bombi and Apicystis bombi – in the colonies.
They also discovered three honeybee parasites – Nosema apis, Ascosphaera apis and Paenibacillus larvae – along with two other parasites that affect both types of bee – Nosema ceranae and deformed wing virus.
Lucy Rothstein, chief executive of the Bumblebee Conservation Trust, said: “Not many people realise how many bees are imported to this country.
“There are something like 70 food crops that are dependent on bees for their pollination which is why this happens.
“This is going to become a major issue for us and we think perhaps even more important than the neonicotinoid pesticides.
“It is a question of looking at what the solutions are and taking steps to bolster the regulations.”
Source: The Telegraph