Signs of Decline: First Honeybees, Now Bumblebees

As with colony collapse disorder in honeybees, the causes of bumblebee decline are not scientifically defined and might be a combination of factors. The honeybee disorder, sometimes called CCD, has galvanized the global scientific community, given the honeybee's importance to crop pollination. The Xerces Society is assembling the data of approximately 30 scientists in North America to document the state of the bumblebee, which is also an important pollinator.

"You look at all their data and what we see is really discouraging," said Scott Hoffman Black, the society's executive director. "It's a picture of a really drastic decline toward extinction."

Black and Vaughan say they hope the public's growing awareness of the honeybee's plight will spill over to the bumblebee and other native bees that might be in trouble.

Vaughan said the decline of many bumblebee species has engendered a number of theories, including habitat loss and the commercial rearing of bumblebees for crop pollination. The vibration of bumblebee wings is so violent that it causes the pollen from one bloom to shake onto another. This "buzz pollination" is particularly effective in fertilizing tomatoes, cranberries and blueberries. Commercial breeders took species of American bumblebees to Europe to perfect breeding techniques and then brought them back to the United States. Researchers theorize that these bees caught a disease from European bumblebees and have spread it to wild populations via escapees from commercial greenhouses.

Meanwhile, Colla is studying the effects of a relatively new class of pesticides called neonicotinoids, which were introduced in the early 1990s. The pesticides have been linked to the vanishing honeybees. Colla, in lab tests on bumblebees, said that when given doses as low as 12 parts per billion, "they can barely move." The chemical affects the development of the queen bee's ovaries, she said.

Can home gardeners help? Sort of. "We don't have a smoking gun yet," Vaughan said. "Because the declines are so widespread, it signifies to us there's some sort of disease" beyond the control of the homeowner. But the gardener can take steps to help the bumblebee.

By planting lots of flowers that the bumblebee likes, "you're strengthening the immune system, strengthening their ability to produce more young," he said. The society's Web site lists shrubs, perennials and herbs that the gardener can plant to feed bumblebees, including asters, joe pye weed, blueberries, sunflowers, sedums, borage, hyssop and marjoram. (At http://www.xerces.org, go to "Xerces Publications," then "Fact Sheets About Native Pollinators," then "Plants for Native Bees in North America.")

The second thing is to minimize the use of pesticides, especially when bees are on the wing. It is also up to a homeowner to monitor spraying by a landscape maintenance company.

"Most people don't know the difference between a bumblebee or a honeybee," Black said, "but we are seeing, since CCD reared its head, more and more people interested in the subject."

But the plight of the bumblebee is still relatively unknown. "They are small animals; people don't think about it," he said. "People are thinking about high gas prices and the war in Iraq."