Decimation of Bee Colonies Has Various Possible CausesScientists are working hard to understand the sources of a staggering decline in honeybees in as many as 27 U.S. states and countries in Europe and Asia this winter, said Cornell associate professor of entomology Nicholas Calderone, during a media teleconference May 10.In the United States, half a million to a million colonies out of a total 2.4 million colonies have died this winter. Both tracheal mites (Acarapis woodi) and varroa mites (Varroa destructor) have threatened the bee industry since the 1980s, causing similar catastrophic die-offs to bee populations in the winters of 1995-96 and 2000-01. The mites feed on U.S. honeybees and act as a vector for a number of bee viruses, though varroa mites are especially deadly. While many bees this year exhibit symptoms of mite damage, about 25 percent of the deaths this year cannot be attributed to mites or any other known honeybee pest, Calderone said

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