Pesticide link to colony collapse called overblown

Recently published papers that have drawn a direct link between insecticides and declining bee populations don’t apply to Canadian bees, say scientists in Ontario and British Columbia.

Studies released in the last four weeks based on research in France, Britain and Harvard University determined that a popular insecticide is killing bees.

The studies concluded that neonicotinoids interfere with bees’ homing skills, hampers the insect’s ability to reproduce and may be a primary factor behind colony collapse disorder.

Neonicotinoids are used for insecticidal seed treatments and sprayed on crops. Imidacloprid, a Bayer Crop Science neonicotinoid, is registered for use on more than 140 crops in 120 countries.

The studies have led to sensational headlines in prominent media outlets, but Ernesto Guzman, a University of Guelph entomology professor, said scientists and the public shouldn’t be shocked.

“Would they (scientists) expect to find a different outcome? If you’re putting a poison in a syrup that you feed the bees with, would you expect something different?” said Guzman, head of the Guelph Honey Bee Research Centre.

“If finding that a pesticide kills bees, it (may be) new and surprising to some, it’s not to me. That’s what pesticides were designed for, to kill insects.”

Guzman said most entomologists agree that insecticides are partially, but not completely responsible, for bee losses.

“The only thing we, bee scientists, agree upon is that this is a multi-factor problem. It’s not a single cause,” he said.

“What we don’t agree upon is the relative weight of each factor. To us, in Canada, factor number one is varroa (mites).”

Canadian bee colonies have been dying off at rates of 30 to 40 percent since about 2006, which is much higher than the historical over-wintering losses of 15 per cent.

Leonard Foster, a bee expert and biochemistry professor at the University of British Columbia, said the culprits are varroa mites, the viruses transmitted to bees from the mites, the nosegay fungus and poor bee management.

He said insecticides seldom harm bees in the natural environment because they don’t encounter insecticide concentrations high enough to cause damage.

There have been a few cases where bees were accidentally exposed and killed by concentrated doses of pesticides, but he said the media response to the British, French and Harvard studies has been excessive.

“I’d say it’s very much overblown,” he said.

“In most cases, in the natural environment, where bees are flying around, they very rarely are going to encounter levels of those insecticides to get those effects that people are seeing in labs.”

According to studies at his lab in Guelph, the varroa mite was the principle cause of bee colony losses, followed by weak colony population going into the winter.

Insufficient bee feeding was the number three cause.

More bee colonies will survive in Canada if beekeepers can find a way to manage those factors, Guzman said.

Ambient pesticide exposure is well down the list of factors, or possibly even a non-factor, he added.

However, Guzman said neonicotinoids might be killing bees in other countries.

“Maybe it’s different in other parts of the world. I’m sure that where they spray lots of pesticides, the ranking (significance) of pesticides would be much higher than here.”

However, a neonicotinoid ban isn’t going to save Canadian bees, Guzman said.

“My sense is that we will need to find local solutions … or at least, regional solutions.”

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