Wild ground-nesting bees might be exposed to lethal levels of neonics in soil

Date: August 26, 2019

Source: University of Guelph

In a first-ever study investigating the risk of neonicotinoid insecticides to ground-nesting bees, University of Guelph researchers have discovered at least one species is being exposed to lethal levels of the chemicals in the soil.

Examining the presence of these commonly used pesticides in soil is important given the majority of bee species in Canada make their nests in the ground.

This study focused on hoary squash bees, which feed almost exclusively on the nectar and pollen of squash, pumpkin and gourd flowers.

Researchers found that the likelihood that squash bees are being chronically exposed to lethal doses of a key neonicotinoid, clothianidin, in soil was 36 per cent or higher in squash fields.

That means 36 per cent of the population is probably encountering lethal doses, which is well above the acceptable threshold of 5 per cent, in which 95 per cent of the bees would survive exposure.

"These findings are applicable to many other wild bee species in Canada that nest on or near farms," said U of G School of Environmental Sciences professor, Nigel Raine, who holds the Rebanks Family Chair in Pollinator Conservation and worked on the study with PhD student and lead author Susan Chan.

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