The following correction was printed in the Guardian's Corrections and clarifications column, Friday April 20 2007

In the article below, we should have written Mary, not Marie, Celeste. This has been corrected.

When John Chapple, one of London's largest keepers of honeybees, opened his 40 hives after the winter, he was shocked: 23 were empty, seven contained dead bees, and only 10 were unaffected by what seemed to be a mystery plague.

Beekeepers are used to diseases sweeping through their colonies, and, nationally, nearly one in seven colonies dies naturally each winter. But this seemed very different to Mr Chapple, who is head of the London Beekeepers Association and has 20 years' experience with the insects and their diseases.

"The problem was that most of the bees had just disappeared. It was like the Mary Celeste. There was no chance they had been stolen," he said yesterday. "The ones that were left did not seem to have been attacked by varroa [the tiny parasitical mite that beekeepers have learned to live with since it arrived from Asia 15 years ago]. I really do not know what happened".

Mr Chapple's experience has chimed with other beekeepers. "Many colleagues and bee clubs tell me that they are experiencing something similar. The Pinner and Ruislip beekeepers' group told me only this morning that they have lost 50% to 75% of their bees. I don't know what is happening, but the bees are just going," he said.

Many British beekeepers fear they are witnessing the start of an alarming phenomenon which is sweeping the US and Europe. Colony collapse disorder (CCD) is possibly the most serious disease yet faced by bees.

According to the national bee unit, a branch of the Department for Environment, Food and Rural Affairs, its "symptoms appear to be the total collapse of bee colonies, with a complete absence of bees or only a few remaining in the hive". The unit says no one has any idea what is causing CCD. Theories in the US, where 24 states are affected and losses of 50% to 90% of colonies are being reported, include environmental stresses, malnutrition, unknown pathogens, the use of antibiotics, mites, pesticides and genetically modified crops.

Because bees pollinate millions of hectares of fruit trees and crops, the implications for agriculture are enormous. "Approximately 40% of my 2,000 colonies are currently dead and this is the greatest winter mortality I have ever experienced," Gene Brandi, a member of the California State Beekeepers Association, told the US Congress recently.

In Spain, thousands of colonies are said to have been lost, and up to 40% of Swiss bees are reported to have disappeared or died in the past year. Heavy losses have also been reported in Portugal, Italy and Greece.

Government bee inspectors met yesterday, but Mike Brown, head of the national bee unit based in York, reported no signs of CCD in Britain. "There is no evidence in the UK right now of colony collapse disorder," he said in a statement. "The majority of inspectors said that they can put the current mortalities in honeybee populations around the UK down to varroa or varroasis."

"I just don't know where they get their information," said Mr Chapple. "They took away some of my bees but I have heard nothing. All I know that something is very wrong with our bees."