Condemned cells

A killer disease continues to wipe out honey bee colonies across America, and British beekeepers say that their hives are now starting to succumb. While everything from pesticides to mobile phones is being blamed, Richard Grant joins investigators hunting for the real culprit

'These are some of the sickest bees in America,' says Dennis vanEngelsdorp, helping me into a beekeeper's suit but wearing just a T-shirt, jeans and sandals himself. A scruffy blond Dutch-Canadian, 37, and a casual veteran of many thousand bee stings, he is one of the lead scientists investigating the mysterious die-off of honey bees in America. He has been inspecting hives around the country, bringing back samples for the various laboratories studying the phenomenon and keeping some of the worst cases under observation here by his cabin in the woods of central Pennsylvania.

	Sweet turned sour: bees are vanishing in huge numbers

He opens the bear-proof fence and works the bellows on his smoker, a nozzled canister full of burning leaves. Smoke makes bees less aggressive. It disrupts the scent alarms sent by the guard bees, instructing the others to come out and attack the intruders. Instead they start gorging themselves on honey, on the assumption that a forest fire is about to destroy the hive and they'll need the extra energy to build a new one. He puffs some smoke into the first hive, takes off the lid and lifts out one of the frames. 'Look at this,' he says, 'This should be covered in bees. There's plenty of honey, pollen and brood [eggs, larvae and pupae] but hardly any adults, just these few small groupings. They're abandoning their young and their food stores, leaving the colony and just disappearing.'

Honey bees cannot survive outside the sophisticated social structure of the colony, with its guard bees and nurse bees, heating and cooling teams, cleaning squads, foragers, comb-builders, honey-processors - all of them female and all of them sisters, daughters of the same queen, communicating with each other with scents and through dances. The males, or drones, are big, hairy, clumsy and stingless. They don't dance and their only function is to mate with the queen, after which they die.

The investigators have no doubt that the disappearing bees are dying but they almost never find the dead bodies, which doesn't make it easy to determine what's causing the phenomenon. For want of a better term, they're calling it Colony Collapse Disorder (CCD), and since last November it has ravaged a quarter of America's 2.4 million beehives. In mild cases 35 per cent of the bees disappear. In severe cases an apparently healthy colony of 30,000 bees will empty itself out completely in a few days. 'Some people think their navigation systems are affected and the bees are getting lost on their way back to the hive,' vanEngelsdorp says. 'I think the bees know they're sick and they're leaving the colony so they don't infect the others. But that's just a theory. At this stage it's all just theory although we are narrowing down the possible explanations.'

He lifts the lid off another hive. This one is completely deserted but still contains a good supply of honey and an intact comb. 'It's been like this for more than two weeks,' he says. 'Normally, within a day or two of bees leaving a hive, other bees come in to rob the honey and small hive beetles and wax moths start eating the comb. But this hasn't been touched and it's something we see a lot with CCD. The toxin or the pathogen or whatever it is must still be giving off a scent. These insects can detect it but as yet we can't.'

A third hive contains only the slender elegant queen, still laying eggs, and a small surrounding cluster of her newly hatched offspring. 'It doesn't seem to affect the queens. Look, she's really trying but the adults are leaving faster than she can replace them. Why? That's the big question.'

For American agriculture it's a $14 billion a year question. That is the estimated value of the food crops pollinated by honey bees every year - 90 different fruits and vegetables, or one third of the American diet. They also make honey, of course, but in economic terms that's strictly a sideline activity, valued at $157 million a year. 'Without bees for pollination,' vanEngelsdorp says, 'we'd basically be eating grains and meat.'

Colony Collapse Disorder has generated enormous public interest and media coverage in America and dozens of theories have been proposed, including some predictable nonsense: the bees are experiencing rapture and ascending to heaven; aliens are abducting the bees; the military is altering the earth's electro-magnetic field in top-secret experiments; it's a plot by Osama bin Laden to destroy American agriculture.

GM crops have come under more serious scrutiny. So have the possible effects of climate change, air pollution, chemicals in the water and radiation waves from power lines and mobile phones. The main suspects, however, are a new contagious disease, damage from pesticides, and the stress on bees from being transported long distances and fed on artificial syrups and protein supplements. Most commercial beekeepers in America live as nomads, migrating from one flowering crop to the next with their hives stacked up in 18-wheel juggernauts. These were the first to suffer from CCD and the hardest hit, although it is also affecting some small organic beekeepers who don't take their bees on the road.