Monarch butterflies have declined more that 80 per cent over the last two decades and scientists are trying to find out why. (Photo by THE CANADIAN PRESS)

Monarch butterflies have declined more that 80 per cent over the last two decades and scientists are trying to find out why. (Photo by THE CANADIAN PRESS)

Study suggests neonic pesticides harming monarch butterfly eggs

Research published in the Journal of Animal Ecology

A recently published study suggests that one of the world’s most common pesticides may be contributing to the decline of one of its most-loved butterflies.

University of Guelph researcher Ryan Norris conducted one of the first real-world studies on monarch butterflies and so-called neonic pesticides. He says the chemical seems to reduce the number of eggs that successfully hatch.

“It’s the first field evidence that neonics can have a negative impact on larval survival of monarchs,” Norris said in an interview Wednesday.

Monarchs undergo one of nature’s most remarkable migrations, fluttering all the way from Canada to Mexico and back. But their numbers have declined more that 80 per cent over the last two decades and scientists are trying to find out why.

Neonicotinoid pesticides are widely applied to common crops such as corn and often drift onto other plants, including milkweed, which monarchs depend on for nesting and food. Monarchs actually prefer milkweed growing alongside or within cultivated fields, Norris said.

“We don’t know why. But that’s where they get hit the hardest (with neonics).”

The research, published in the Journal of Animal Ecology, involved Norris and his colleagues working with a farmer near Halton, Ont. The farmer planted one half of a small plot with corn seed that had only been treated with a fungicide and the other half with corn that had been coated with clothianidin, a common neonic.

Milkweed was deliberately planted along with the corn to attract monarchs.

Over two years, the scientists found that monarch eggs on the neonic plot had a three per cent less chance of successfully hatching. It sounds small, said Norris, but with the large number of eggs monarchs lay, it adds up to big numbers.

“(That) could easily mean millions of larvae that are dying each year because of the neonics.”

Neonics are increasingly implicated in plummeting numbers of pollinators such as bees. The chemicals are banned in the European Union and in some U.S. states.

In 2018, Health Canada proposed to tightly restrict the use of neonics, including a ban on all outdoor applications of clothianidin. It is currently re-evaluating that stance and is expected to announce an updated decision next spring.

Millions of monarchs migrate each winter to a small area of mountaintop forest in central Mexico, where scientists estimate their population by measuring the area of trees turned orange by the clustering butterflies. That area has shrunk to just over two hectares, down 26 per cent from last year, says the Centre for Biological Diversity.

Monarchs are considered a species of special concern in both Canada and Mexico.

The black-and-orange butterflies face many threats other than pesticides, Norris said, but pesticides seem to be part of the problem.

“This is yet another piece of evidence of how neonics can influence the biodiversity on our landscape,” he said. “They are having a serious negative impact.”

Although monarchs aren’t important pollinators, that’s not the only measure of a species’ value, Norris suggested.

“Monarchs, in many people’s minds, represent butterflies,” he said. “When they think butterflies, they think monarchs.

“They serve a really important role as a connection for people to butterflies and to nature.”

This report by The Canadian Press was first published May 13, 2021.

Agriculture

Just Posted

Alberta Premier Jason Kenney arrives at the 2021 budget in Edmonton on Thursday, Feb. 25, 2021.THE CANADIAN PRESS/Jason Franson
Alberta launches COVID vaccine lottery with million-dollar prizes to encourage uptake

The premier says the lottery will offer three prizes worth $1 million a piece, as well as other prizes

Dharmesh Goradia, and his daughter Vidhi and wife Chaitali, at the 2017 festival for the Godess Durga, held at the Golden Circle. (Photo contributed)
Draft curriculum misses the mark for central Alberta Hindu society

Meeting scheduled with Alberta Education officials

Air Canada planes sit on the tarmac at Pearson International Airport during the COVID-19 pandemic in Toronto on Wednesday, April 28, 2021. Air Canada says it will recall more than 2,600 employees who were furloughed during the COVID-19 pandemic. THE CANADIAN PRESS/Nathan Denette
Alberta’s tourism sector hurt by COVID-19 pandemic: ATB Financial

Between border closures, public health measures and hesitancy to travel, Alberta’s tourism… Continue reading

Canadian Prime Minister Justin Trudeau participates in a plenary session at the G7 Summit in Carbis Bay, England on Friday June 11, 2021. THE CANADIAN PRESS/Adrian Wyld
Canada donating 13M surplus COVID-19 vaccine doses to poor countries

Trudeau says the government will pay for 87 million shots to be distributed to poor countries

Indigenous Services Minister Marc Miller is seen during a news conference, Wednesday May 19, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld
Indigenous child-welfare battle heads to court despite calls for Ottawa to drop cases

Feds are poised to argue against two Canadian Human Rights Tribunal rulings

The Great Ogopogo Bathtub Race has been held in Summerland as a fundraising event. Do you know which Canadian city introduced this sport? (Black Press file photo)
QUIZ: A summer’s day at the water

How much do you know about boats, lakes and water?

A man wears a face mask as he walks by a sign for a COVID-19 vaccination site in Montreal, Sunday, May 16, 2021, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes
Canada paid a premium to get doses from Pfizer earlier than planned

OTTAWA — Canada paid a premium to get more than 250,000 doses… Continue reading

The Kamloops Indian Residential School in Kamloops, B.C., is shown in this 1930 handout photo. HO — Deschatelets-NDC Archives
Calls grow for Ottawa to review settlement decisions for residential school survivors

Lawyer Teri Lynn Bougie still cries when she talks about the final… Continue reading

Syringes are readied at a COVID-19 mobile vaccination clinic for members of First Nations and their partners, Friday, April 30, 2021 in Montreal. Most of the federal contracts for COVID-19 vaccines allow for Canada to donate some of its doses to other countries or international aid organizations and in at least three cases, for the doses to be resold.THE CANADIAN PRESS/Ryan Remiorz
Canada’s vaccine contracts allow for doses to be donated, in some cases resold

OTTAWA — Most of the federal contracts for COVID-19 vaccines allow for… Continue reading

Grand Chief Stewart Phillip, President of the Union of British Columbia Indian Chiefs, responds to the report on the National Inquiry into Missing and Murdered Indigenous Women and Girls, in Vancouver, on Monday June 3, 2019. As stories of the horrors of residential schools circulate after the Tk'emlups te Secwepemc First Nation announced it had located what are believed to be the remains of 215 children, Grand Chief Stewart Phillip of the Union of B.C. Indian Chiefs said he feels a connection with the former students. THE CANADIAN PRESS/Darryl Dyck
Two sides of the same coin: Ex-foster kids identify with residential school survivors

VANCOUVER — As stories of the horrors of residential schools circulate after… Continue reading

A woman sits and weeps at the scene of Sunday's hate-motivated vehicle attack in London, Ont. on Tuesday, June 8, 2021. Four members of a family in London, Ont., are set to be buried today. The public has been invited to help celebrate the lives of Talat Afzaal, 74, her son Salman Afzaal, 46, his wife Madiha Salman, 44, and their 15-year-old daughter Yumna Salman.THE CANADIAN PRESS/ Geoff Robins
Funeral to be held today for London family killed in attack

LONDON, Ont. — Four members of a Muslim family killed in what… Continue reading

Canadian Prime Minister Justin Trudeau and United States President Joe Biden listen to United Kingdom Prime Minister Boris Johnson deliver opening remarks at a plenary session at the G7 Summit in Carbis Bay, United Kingdom Friday June 11, 2021. THE CANADIAN PRESS/Adrian Wyld
Trudeau to discuss foreign policy with G7 leaders at second day of summit meeting

CARBIS BAY, CORNWALL, ENGLAND — Foreign policy is on the agenda for… Continue reading

Most Read