WASHINGTON — Fewer honeybee colonies died last winter, but mortality rates remain a cause for concern, according to a national survey released earlier this month.
Beekeepers across America reported 23.2 percent of their colonies died between Oct. 1 and March 31 in a survey conducted jointly by the Bee Informed Partnership, the Apiary Inspectors of America and the U.S. Department of Agriculture. Since the winter of 2007-08, the die-off rate has been below 29 percent only one other year, in 2011-12, when it was 21.9 percent.
Ideally, only 10 percent of colonies would die off during a given winter, said Ramesh Sagili, an apiculturist, or bee expert, with Oregon State University. But the large die-offs of recent years have caused beekeepers to adjust their expectations upwards in terms of mortality, he said. Compared to 30 percent, a die-off rate of 22 percent, which is where Oregon’s colony mortality rate has hovered in recent years, seems reasonable, he said.
“It’s not still a very good number,” he said. “Anything above 15 percent is not sustainable for a beekeeper.”
While bees are primarily associated with the honey they produce, they also play a crucial role in pollinating many crops that serve as human food, he said. As much as one-third of the food we eat, including fruits and vegetables, is pollinated by bees, he said.
Many products grown in Oregon, including pears, apples, cherries, and blueberries, rely on bees to pollinate the trees and bushes.
Bees also pollinate seeds for many additional crops, including carrots, broccoli, mustard, onions, cauliflower and cabbage, among others.
Many nut trees also rely on bees for pollination, including 850,000 acres of almond trees in California, he said.
“Bees do an amazingly important job of pollinating these crops and getting these foods to our table,” he said.
All told, $15 billion worth of food is pollinated by bees each year, according to the Natural Resources Defense Fund.
A number of factors, including parasites, malnutrition, and widespread use of pesticides and fungicides, have contributed to colony mortality, Sagili said.
In particular, varroa mites, which suck on bees’ blood and transmit viruses into colonies, require careful attention from beekeepers, he said. When the deadly mites were introduced to the United States in 1987, most beekeepers could get away with visiting their hives once a month, he said.
Now, hives need to be tended at least weekly, he said.
“Management costs have increased,” he said. “There are a lot of management practices that a beekeeper has to go through. They have to keep these mites under control.”
The widespread disappearance of bees began in 2006, and has been labeled colony collapse disorder. An article published this month by the Bulletin of Insectology linked colony collapse disorder to exposure to certain pesticides, although critics suggest the study’s authors exposed hives to more chemicals than they would likely encounter in the wild.
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