British beekeepers are viewing the forthcoming opening of their hives with a certain amount of anxiety; unsure if their colonies have survived the winter.

The cause of their concern is a mystery ailment which has wiped out "thousands" of honeybee colonies across the northern hemisphere. Beekeepers across 24 US states are already reporting "heavy losses" to "Colony Collapse Disorder", which has in recent years hit hard in Greece, Italy, Poland, Portugal, and Spain.

No one knows the cause of Colony Collapse Disorder, which has been attributed to various possible causes. Dr Max Watkins, technical director of honeybee health specialist Vita, explained: "The situation is very serious, but no one yet understands the cause of these widespread honeybee colony deaths. Alleged causes range from harmful pesticides and increased solar radiation through ozone thinning, to falling queen fertility and use of unauthorised bee treatments.

"We really don't know the answer - several causes may be at work and the only common factor known so far is that many honeybee colonies are dying. The phenomenon is alarming especially because agricultural pollination and therefore crop production levels are threatened."

Symptoms of Colony Collapse Disorder are normally evident between late summer and early spring. In the US, colonies have been hit as older bees pop their clogs, "leaving behind the queen and young workers not yet ready to forage for pollen and nectar and insufficient in number to maintain the colony", as Vita explains.

In the UK, meanwhile, there have been "a few but significant examples" of what experts call the "Marie Celeste phenomenon" - colonies abandoning hives altogether leaving no evidence of what caused their disappearance.

Watkins continued: "It's a real mystery. We need beekeepers to report their losses and examine and analyse their colonies thoroughly. In the USA it has been difficult to obtain adequate samples and sufficient detailed reports. From records that are available, however, it is noticeable that many beekeepers have been using unauthorised treatments for varroa mites, a honeybee parasite. I'm sure that this is not the complete explanation, but it may be a significant contributory factor."

Whatever the cause of Colony Collapse Disorder, European honeybees face a concrete threat from hordes of killer Asian Hornets, which can wipe out a nest of 30,000 bees "in a couple of hours" in search of larvae on which to feed their young.

The forests of Aquitaine, in south-west France, already boast swarms of the insect assassins which have "spread like lightning" across France and will inevitably, experts say, find their way to the UK at some point. ®