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Even if pesticides are a big part of the bee-death mystery, there are other suspects. Beekeepers have always had to protect their charges from dangers such as the American foulbrood--a bacterial disease that kills developing bees--and the small hive beetle, a pest that can infiltrate and contaminate colonies. Bloodiest of all is the multidecade war against the Varroa destructor, a microscopic mite that burrows into the brood cells that host baby bees. The mites are equipped with a sharp, two-pronged tongue that can pierce a bee's exoskeleton and suck its hemolymph--the fluid that serves as blood in bees. And since the Varroa can also spread a number of other diseases--they're the bee equivalent of a dirty hypodermic needle--an uncontrolled mite infestation can quickly lead to a dying hive.
The Varroa first surfaced in the U.S. in 1987--likely from infected bees imported from South America--and it has killed billions of bees since. Countermeasures used by beekeepers, including chemical miticides, have proved only partly effective. "When the Varroa mite made its way in, it changed what we had to do," says Jerry Hayes, who heads Monsanto's commercial bee work. "It's not easy to try to kill a little bug on a big bug."
Other researchers have pointed a finger at fungal infections like the parasite Nosema ceranae, possibly in league with a pathogen like the invertebrate iridescent virus. But again, the evidence isn't conclusive: some CCD-afflicted hives show evidence of fungi or mites or viruses, and others don't. Some beekeepers are skeptical that there's an underlying problem at all, preferring to blame CCD on what they call PPB--piss-poor beekeeping, a failure of beekeepers to stay on top of colony health. But while not every major beekeeper has suffered catastrophic loss, colony failures have been widespread for long enough that it seems perverse to blame the human victims. "I've been keeping bees for decades," says Doan. "It's not like I suddenly forgot how to do it in 2006."
There's also the simple fact that beekeepers live in a country that is becoming inhospitable to honeybees. To survive, bees need forage, which means flowers and wild spaces. Our industrialized agricultural system has conspired against that, transforming the countryside into vast stretches of crop monocultures--factory fields of corn or soybeans that are little more than a desert for honeybees starved of pollen and nectar. Under the Conservation Reserve Program (CRP), the government rents land from farmers and sets it aside, taking it out of production to conserve soil and preserve wildlife. But as prices of commodity crops like corn and soybeans have skyrocketed, farmers have found that they can make much more money planting on even marginal land than they can from the CRP rentals. This year, just 25.3 million acres (10.2 million hectares) will be held in the CRP, down by one-third from the peak in 2007 and the smallest area in reserve since 1988.