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Bumblebees and their cousins, the honey bee, have been dying off
at alarming rates. In particular, honey bees, which are critical
agents in the pollination of important U.S. crops, disappeared
at a staggering rate over the last year when losses of managed
bee colonies topped 42 percent year-on-year in April.
Scientists, consumer groups and beekeepers have pinned much of
the blame on pesticide use.
But the bees found dead in Oregon this month may have been
reacting to a natural agent, said Dale Mitchell, pesticide
program manager with the Oregon Department of Agriculture.
“In all four incidents, bees were found near one species of
tree,” Mitchell said. “We have no indication that pesticides
were used on the linden trees where they were found, but there
has been some research suggesting that the bumblebee is not able
to process the nectar in these trees.”
The linden tree originated in Europe, and North American
bumblebees may not be able to handle a chemical that occurs
naturally in its nectar, a hypothesis researchers at Oregon
State University are exploring, Mitchell said.
He would not rule out the possibility that pesticides may also
have played a role in the recent Portland deaths.
In 2013, more than 50,000 bees dropped dead at an Oregon Target
store whose parking lot was filled with lindens that had been
treated with insecticides, prompting state officials to restrict
use of the neonicotinoid class of pesticides, which has been
identified as a major source of bee colony collapses elsewhere
in the world.
Since those restrictions went into effect, fewer massive-scale
bee die-offs have been reported in the state, Mitchell said.
(Editing by Cynthia Johnston and Ken Wills)
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