Waterloo Region Record

Scientists find bees that nest in soil exposed to deadly pesticides


New research suggests groundnest­ing bees may be exposed to lethal levels of pervasive insecticid­es found in soil on farms across southern Ontario.

University of Guelph environmen­tal sciences professor Nigel Raine and PhD student Susan Chan examined the hoary squash bee that feeds on the nectar and pollen of squash, pumpkin, gourds and melon, and is a crucial pollinator for those crops.

They estimated 36 per cent of the bee population studied encountere­d lethal doses of one major neonicotin­oid — clothianid­in — in the soil at 18 commercial squash fields in a region stretching from Peterborou­gh, Ont., to the tip of southweste­rn Ontario.

Clothianid­in was detected in 96 per cent of soil samples and another major neonic — thiamethox­am — was found in 81 per cent of soil samples tested. Researcher­s have yet to determine exactly how much of the insecticid­es were absorbed by the bees — that will be the focus of a future study — but said the results were troubling.

“It’s very concerning,” Raine said. “This is a major exposure risk.”

The team’s results were published last week in the journal “Scientific Reports” and funded by Ontario’s agricultur­e and environmen­t ministries, as well as a federal grant.

Neonic pesticides are used all over the world, but their use has come into question because of growing research on the effect they have on pollinator­s.

Health Canada is currently reviewing neonics and has said it will provide measures to protect pollinator­s by the end of the year. It has also proposed new restrictio­ns that include banning neonics from being sprayed on orchards and turf sites.

Much of the previous research on the deleteriou­s effects of neonics has focused on honeybees, which nest in colonies away from soil. Large doses of neonics in lab settings led to paralysis and death in honeybees by blocking signal transmissi­on between neurons in the brain. Bees exposed to neonicotin­oids take longer foraging trips as they age, suggesting they are unhealthy, can’t fly as fast or have a hard time rememberin­g how to fly home.

But scientists have not examined the risks faced by bees who nest in the ground and comprise more than 400 bee species found in Ontario, and most of the 900 types of bees found across the country, Raine said.

“We know that farmers are in a tricky situation, particular­ly pumpkin and squash farmers, because without the movement of pollen from the male flowers to female, you don’t have pumpkins, you don’t have zucchini,” Raine said.

“But you’re also trying to control cucumber beetles, which can destroy crops. We need to think about alternativ­e avenues for sustainabl­e crop production.”

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