Varroa mite control closer to reality

LINDELL BEACH, B.C. – A new discovery could pave the way for more effective chemicals to protect honeybees from the deadly varroa parasite.

Researchers at Michigan State University have figured out how to produce proteins in the laboratory that help channel sodium ions through cell membranes of the varroa mite.

The findings, which could lead to a more effective control of the mites, were published recently in the Journal of Biological Chemistry.

“The insecticide used to control varroa mites, fluvalinate, targets the mite sodium channel,” said Ke Dong, MSU professor of entomology.

“But the mites are becoming resistant to fluvalinate. Successfully producing the mite sodium channel in the lab now allows scientists to develop new chemicals that target the mite sodium channel but don’t affect the honeybee.”

Fluvalinate paralyzes the mite and kills it, but it can harm the bees and contaminate honey if it is not used with extreme care.

Researchers also discovered two amino acids in the mite sodium channel that make it resistant to a deadly poison called tetrodotoxin, which is found in puffer fish.

“This research opens the door for more applied research on chemicals to control mites and pest insects,” Dong said.

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According to an Alberta Beekeepers Commission report released in April 2009, the value of honeybee pollination is worth $1.3 to $1.7 billion a year in Canada and $15 billion in the United States.

Canadian honey production is worth $122 million a year in Canada, but total production has dropped in recent years, falling in 2008 to its lowest level in 12 years.

The timeline coincides with the recently identified and devastating colony collapse disorder.

Canadian honeybee overwintering losses increased from 29 percent in 2006-07 to 35 percent in 2007-08, according to data from the Canadian Association of Professional Apiculturists.

That is more than double the long-term normal loss of 15 percent experienced before varroa mites appeared in Canada.

The parasite, which originated in the eastern hemisphere, first appeared in Canada in the late 1980s in Manitoba and New Brunswick along the U.S. border. It first appeared in the United States in 1987.

“Beekeepers routinely lose 50 to 100 percent of their colonies in Michigan,” said Zachary Huang, an associate professor and long-time

collaborator with Dong on mite sodium channels.

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“I largely suspect varroa mites. My research apiary had a 90 percent loss last winter. The average in Michigan and in the U.S. nationwide has always been 30 to 50 percent, though, because it usually evens out with some beekeepers losing only 10 to 20 percent.”

Vancouver Island beekeepers also experienced a 90 percent loss of their hives this winter, possibly because of a lethal combination of parasites and last year’s long hot summer.

“It was a perfect storm,” said B.C. provincial apiculturist Paul van Westendorp.

“When you have a late summer (like 2009) and the bees expend a great deal of effort and energy taking more nectar, you basically zap the strength out of that generation of bees destined for the winter population,” he said.

“This could have caused the colonies to be weaker than they should have been. Varroa mites are very damaging. They have proven to be very successful vectors in transmitting bee viruses.”

The mites can kill an entire honeybee colony within a year, feeding on bee blood similar to mosquitoes.

In 2004, they were responsible for wiping out nearly 50 percent of the U.S. commercial honeybee population.

“These mites are a big, big problem for agriculture,” Huang said. “Nearly 80 percent of food crops depend on pollination.”

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More research remains to be done before Dong’s findings result in a new generation of chemical control of the varroa mite.