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Honeybees’ Stressful Lives
In the 1980s, two deadly parasitic mites spread across the United States, wreaking havoc on both managed and feral honeybees. Between 1981 and 2005, the number of commercial honeybee colonies dropped by about a third, with many of the losses attributable to the mites. Other diseases and pests have also taken their toll, as has competition from aggressive Africanized bees, which have spread through several southern U.S. states, including southern California, since the early 1990s.

In fall 2006 beekeepers began reporting another calamity: they were finding many hives empty except for the queen, a few young adult bees (and then only sometimes), and the brood--eggs, larvae, and pupae. Plentiful food remained, however, and no dead bees were found either in the hives or nearby. Normally, other insects would immediately move in to take the food of a severely weakened or dying colony, but with CCD this “robbing” is delayed, suggesting that other insects were avoiding the abandoned hives.

Sporadic incidents of hive abandonment have occurred in the past, but nothing on the present scale has been reported. “This is the worst,” Fore said. So far it seems that the beekeepers suffering the heaviest losses are large-scale commercial operations that truck their hives from state to state to pollinate various crops.

Shortly after the first reports of CCD, a working group was formed to study the phenomenon, develop strategies to address it, share and disseminate information, and raise funds for research. The Colony Collapse Disorder Working Group brought together university researchers, agricultural extension educators, and state regulatory officials. Researchers are looking at several possible causes, including parasites and diseases, pathogens, poor nutrition, lack of genetic diversity of bees, increased levels of stress in adult bees, and chemical contamination.

One theory gaining ground among researchers is that a combination of causes has pushed bee colonies beyond their ability to recover. “We think this could be the ‘perfect storm’ for bees,” said Kevin Hackett, who leads the research programs on bees and pollination for the U.S. Department of Agriculture’s Agricultural Research Service (ARS). “It could be the tipping point, where the colonies just can’t fight back.”

Many commercially managed honeybees live stressful lives. Commercial beekeepers today often have thousands of hives--the biggest have as many as 60,000--and a healthy hive may house 50,000 to 60,000 adult bees in summer, at the peak of their population. During pollination season (which varies depending on the crops being served), many beekeepers pack their hives onto trucks and transport them for hundreds, sometimes thousands, of miles. “They’re never really in one spot for long,” said Rodney Gubbels, a small-scale beekeeper who has 2,000 or so hives based near Livermore, in Contra Costa County, and trucks his bees to crops in California and Oregon.

In transit bees go without food or water and may suffer from both hot and cold weather. If conditions are poor when the bees arrive--if there’s been a drought that’s reduced the floral resources, for example, or weather conditions are bad--the colonies can be further weakened by malnutrition. Added to that are the pesticides and other chemicals that bees are often subjected to, which may not kill them outright but can contaminate nectar or pollen in the hive. “Bees are always picking up something--whatever people spray,” Gubbels said. A newer class of nicotine-based pesticides is suspected of interfering with the bees’ ability to forage and navigate.

All these factors can weaken the bees’ immune systems and leave them more vulnerable to disease. Beekeepers have always lost colonies over the winter, when the bees’ populations are at their lowest and most vulnerable, according to Fore. “Bees die all the time. But 10 percent winter loss used to be bad; now 15 to 20 percent isn’t unusual.”

“The bottom line is that this shows us how fragile all pollinator systems are,” said Laurie Davies Adams, executive director of the Coevolution Institute, which promotes conserving biodiversity through land stewardship, and coordinator of the North American Pollinator Protection Campaign, a coalition of researchers, conservation and environmental groups, private industry, and state and federal agencies that works to conserve and protect pollinator populations.

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