Dan Davidson has seen his share of dead bees. Like other beekeepers in North America and Europe, Mr. Davidson opens his hives each spring to find piles of the dead pollinators, which have been under attack from viruses, mites and starvation.
But in the past decade, honey bees have been dying in greater numbers, and in new ways. Winter deaths are rising – the Watford, Ont.-based beekeeper lost a third of his this year – and bees are dying at the hive or in the field.
In early June, Mr. Davidson found a mass of bees twitching and dying on the ground outside the hive on a dairy farmer's field in Southwestern Ontario. Ants were carrying some away. Others were crawling into the long grass. Of the 28 hives, 10 had piles of dead or dying bees.
Two fields away, a farmer had just planted a field with corn, a seed that is coated with a type of pesticide called a neonicotinoid (or neonic) that protects the plant from being eaten by wireworms, white grubs and other pests. Mr. Davidson says the pesticide-laced dust kicked up by the tractor and seed planter are responsible for the dead bees. And those not killed by ingesting or carrying the dust back to the hive are at risk of eating pollen that is infused with the pesticide.
Farmers say the seed treatments are essential to protecting their crops against pests, and that the neonicotinoid class is less toxic to humans and animals than older pesticides. They say they need to use the pesticide until studies can show where it is needed, and where it is not.
But there are mounting calls for restrictions on the pesticides. Some scientists say the pesticides that become present in all parts of the plant – including the pollen – are contributing to the declines in populations of honey bees, butterflies and other pollinators. Three types of neonicotinoids have been banned in Europe since December 2013 but remain widely used in North America.
A study released this week found the pesticide poses a "serious risk" to such pollinators as honey bees and butterflies as well as birds and earthworms. The panel of 50 independent scientists, which calls itself the Task Force on Systemic Pesticides, likens the threat posed by neonicotinoids to that of DDT. They say neonicotinoids and fipronil, another widely used pesticide, should be tightly regulated by governments and phased out.
Neonicotinoids have been linked to the deaths of bees in two ways: by being exposed to dust generated by seed planting machinery; and by ingesting insecticide-laced pollen, which weakens them and makes them more vulnerable to deadly viruses.
Other species may also be affected. A biologist at the University of Saskatchewan said in January the chemicals are being found in wetlands in Western Canada, and contributing to the deaths of birds that eat the insects that have ingested the pesticide.
Neonicotinoids were first used in Canada in about 2001, on potatoes. In 2007, the seeds for a wider range of crops began to be treated. Today, the pesticide is used on almost all corn and canola, and half the soybeans, planted in Canada. Beekeepers say only 10- to 20-per-cent of Ontario farmland needs the pesticide, and that its blanket use is overkill.
It is normal to lose 10 to 15 per cent of a bee hive's population each year. But Mr. Davidson and other beekeepers in Ontario began to see losses of 20 to 25 per cent in 2008. Last winter, 40 per cent of beekeepers lost half their bees, according to the Ontario Beekeepers' Association, a group headed by Mr. Davidson.
Barry Senft, chief executive officer of Grain Farmers of Ontario, believes the pesticide is safe. Mr. Senft, who represents which represents 28,000 farmers, says there are no alternatives to neonicotinoids, and that a ban would mean a loss of $600-million worth of crops.
"We know from some of the tests that some of the bee deaths have some neonics in the system. There's no out-and-out study that says absolutely that neonics have caused the death," he said.
Mr. Senft says his group is taking part in a study that will highlight areas in Ontario that are prone to pests. But until that multi-year research is complete, farmers cannot risk losing much of their crops by planting untreated seeds.
There is no doubt high doses of neonicotinoids can kill bees, but it is less clear that the decline in the number of bees is due to the rise in use of neonicotinoids, said Nigel Raine, a professor at University of Guelph, which was the recipient of a recent $750,000 gift from Bayer, one of the makers of the pesticide.
"The jury's still out on what impacts are happening in the field," said Mr. Raine, who recently co-authored a paper that reviewed the effects neonicotinoids have on the health of bees and other insect pollinators. The paper, published in the journal Proceedings of the Royal Society B, called for more studies.
In North America, regulators are moving cautiously on neonicotinoids. Health Canada this year called for a number of changes to the way farmers plant the treated seeds in order to reduce the pesticide-laced dust that is generated, after finding the pesticide "contributed to the majority of the bee mortalities that occurred in corn growing regions of Ontario and Quebec in spring, 2012."
These changes include the use of a wax-based lubricant in corn seed and the fitting of air deflectors on some planting equipment. Such methods have been found to reduce dust by just 20 per cent.
In the U.S., environmental regulators are studying the effects of neonicotinoids, and looking at ways to protect the habitats of pollinators.
The Ontario government has been promoting the planting of seeds that are not coated with neonicotinoids, and seeds that are coated with a fungicide only. The province is spending $1.2-million to study pollinator health and farming practices, and field staff with the Ministry of Agriculture and Food have been analyzing soil conditions to see whether farmers can skip the treatments.
"Bee health is complex, with many contributing factors including loss of habitat, available food supplies, climate change, presence of parasites and diseases, and exposure to toxins such as pesticides. That's why the government has worked with the industry and called on the federal government to work with us to address the important and complex issue of pollinator health," said Mark Cripps, a spokesman for Ontario's Ministry of Agriculture and Food.