An environmental group says it has found banned pesticides on flowers sold at major garden centres in Ottawa, and it has asked the provincial government to investigate possible violations of the Ontario Pesticides Act.

Friends of the Earth Canada, a charitable group based in Ottawa, says garden plants purchased at Canadian Tire, Rona and Home Depot in 2017 have traces of chemicals banned for human health concerns, including a neonicotinoid shown to harm aquatic insects.

Beatrice Olivastri, chief executive officer of Friends of the Earth, said the group bought a range of common garden flowers known to be favoured by native, wild bees – daisies, asters, lavender and others – from five major retailers. The samples were sent to the University of Guelph to test for neonicotinoids, a class of insecticide that includes varieties whose use is banned or restricted in several jurisdictions, including Ontario.

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She said she was surprised to see the results showed some plants contained traces of other herbicides and insecticides known as Class 9 chemicals, including napropamide and spinosad and imidacloprid, a neonicotinoid. Ontario law forbids the use of Class 9 pesticides to kill weeds and bugs around schoolyards, parks, lawns and gardens due to risks to human health.

“I was testing for neonicotinoids and tripped across this. I have to say I’m astonished,” Ms. Olivastri said by phone.

Home Depot declined to be interviewed. “Over the past few years we’ve been in communication with government agencies, the insecticide industry and our suppliers to understand the science, monitor research with a complete phase out of neonicotinoids by the end of 2018,” the company said in an email.

“We are currently investigating the allegations that were raised by Friends of the Earth, as we take these matters very seriously, ” said Valérie Gonzalo, a spokeswoman for Lowe’s Canada, parent company of Rona.

Ms. Olivastri said Rona and Home Depot have shown leadership in working with their growers to rid their garden centres of harmful pesticides, and she was surprised by the results. She said it is possible the stores were unaware their suppliers were using the chemicals, or that the plants were grown in jurisdictions in which the pesticides are legal. “So what? They are selling them to me in this province.”

Canadian Tire did not respond to interview requests.

Plants purchased at Loblaws and Lowe’s stores had either permitted or zero traces of legal chemicals.

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Friends of the Earth has applied to Ontario’s Environmental Commissioner, calling for an investigation to be launched by the Environment Ministry.

“Large corporations like the retailers have control over the types of products they choose to sell, and have control or influence over the behaviour of their suppliers,” reads the group’s application for investigation to the Environmental Commissioner of Ontario.

Gary Wheeler, a spokesman for the Ontario Ministry of Environment, said in an email the government will decide within 60 days if it will launch an investigation after being notified by the Environmental Commissioner.

“We encourage corporations to review their best practices to see if they can take measures to reduce neonics in their products,” he said. “Ontario is committed to continuing to improve pollinator health to protect the health of Ontarians and our environment.”