Bee Colony Collapse May Have Several Causes

By Alexis Madrigal January 8, 2010 | 12:39 pm | Categories: Animals

When suspiciously large numbers of honeybee colonies started collapsing in late 2006, the search began to find the culprit behind the mysterious deaths. Now it seems a whole web of problems may be causing what's known as colony collapse disorder.

It's becoming clear that there is no single parasite, virus or chemical to blame, argues Frances Ratnieks, a bee scientist at University of Sussex in Brighton.

Instead, honeybees are probably dying for all kinds of different reasons from loss of their foraging grounds to increased exposure to global pathogens, Ratnieks wrote in a review of the issue in the journal Science.

"We may conclude that colonies are dying for different reasons in different parts of the world and I would say that if that is the case, I would not be the least bit surprised," Ratnieks told Wired.com.

A variety of pests, viruses and parasites could all be working together to stress the bees. And in some ways, that's worse than trying to take on a single culprit: The problems with beekeeping are systemic, Ratnieks said, and can't be solved with a new pesticide or technique.

In an increasingly globalized world, bee pathogens travel quickly between bee populations. Over the last decades, the Varroa destructor mite has spread from Asian honeybees to the rest of the continents. The gut parasite Nosema ceranae has taken the same path. Both species are believed to make existing bee diseases worse. V. destructor took about four decades, reaching North America about a decade ago. N. ceranae circled the globe in a quarter of that time.

"It is certainly a case in the modern world, pathogens can be transmitted from one corner of the world to an another quickly," Ratnieks said.

He compared the bee pathogen problems to those humans are encountering with swine flu and other emerging diseases, which can spread quickly thanks to modern transportation.

"Even though the U.S. is a big country, what shows up in one part of the country shows up in the other parts of the county in no-time flat," he said.

That's in part because of the economics of beekeeping. The $2 billion almond crop in California requires 1,000,000 honeybee hives for cross-pollination. That's more than 40 percent of all the beehives in the country. So, come almond-tree flowering season, which begins in February, apiarists load up their hives on flatbeds and truck them to San Joaquin Valley. While this pilgrimage may be necessary to keep churning out cheap almonds, it also creates a melting pot of pathogens. And the moving and trucking itself could negatively impact the bees, too.

Ratnieks also suspects that honeybees are more susceptible to disease because their natural forage — weeds and gardens, etc. — has been wiped out by single-crop farming in the major farming valleys of the country.

Add it all up and the honeybees are fighting the battle to survive on several, interconnected fronts.

"It's harder to keep a hive alive now. It used to be with bees in America, if the hive was alive and thriving, chances are the hive would be alive and thriving the next year," said Ratnieks. "Now, they are feeding their hives with supplements and feeding them with chemicals, they are having to peddle quite hard just to keep their hives alive."

Last year, there were enough honeybees to keep the almond trees pollinated, but last summer's weather conditions were bad in North Dakota and the neighboring states where the California hives often spend the season.

With the big almond flowering coming up, and the bees in bad condition, the beginning of next month could harbor a nasty surprise for nut farmers.

"In early February, that's when the rubber hits the road or the shit hits the fan," Ratnieks concluded.

Citation: "Clarity on Honey Bee Collapse?" by Francis L. W. Ratnieks and Norman L. Carreck in Science, 8 JANUARY 2010 VOL 327.

Source: Wired News