Sweetgrass may repel mosquitoes

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This article was published 28/08/2015 (3880 days ago), so information in it may no longer be current.

Sweetgrass, long known as a natural medicine and a sacred plant in indigenous circles, has proven to be as good as DEET in repelling mosquitoes, a new study says.

The report, by the United States Department of Agriculture and its natural-products division, prompted scientific and cultural interest over the last week or two.

“If you hate the pungent odour of mosquito repellents, there might be a sweet-smelling alternative,” noted a freelance article on Smithsonian.com after the study’s presentation at a recent symposium in Boston of the American Chemical Society.

In Winnipeg, news hits lit up social media as indigenous writers took up the new scientific finding.

Sweetgrass is commonly burned and the smoke breathed in during smudges at traditional prayer ceremonies Anyone who’s attended an indigenous event from The Forks to Thunderbird House would be familiar with the sweet vanilla-like scent.

So in Winnipeg, the city known as the native capital of Canada, thousands of people have seen or burned a braid or two of sweetgrass and have long known of its powers.

What tickled interest was how science now recognizes it, too.

Sweetgrass as mosquito repellent: research catches up to native knowledge, was how one headline put it, in the U.S.-based website Indian Country Today.

University of Manitoba associate professor Niigaanwewidam James Sinclair posted the Indian Country Today piece to alert his Facebook network to the study in a light-hearted way.

“Indigenous science is amongst the most innovative and well-versed in the world, and it’s time the world understood this,” said James Sinclair to the Free Press.

The professor and writer is working on an article about indigenous technology, so the study naturally tweaked his interest.

The U.S. government study has almost no commercial value.

The kelly-green coloured grass that shines in the sun isn’t a cash crop, nor is it likely to be. Yet it can be found in fields and along coast lines across North America, making it a plant with a storied folklore history. Interestingly, European folklore also mentions sweetgrass. It was once spread on stone floors in medieval churches to mask odours and repel bugs.

Indigenous folklore from North America is what brought the plant to the attention of the USDA in the first place, lead author Charles Cantrell said from his office at the University of Mississippi.

‘If you hate the pungent odour of mosquito repellents, there might be a sweet-smelling alternative’ — Smithsonian article

Cantrell’s study distilled the essential oil in sweetgrass and tested it by filling vials with a blood-like substance to lure in mosquitoes. Separate vials were covered with filters infused with repellents, including DEET and sweetgrass oil.

The bugs were repelled almost equally by sweetgrass oil and DEET, but DEET won out in the end for lasting longer than the natural oil.

Scientists teased out two chemicals in sweetgrass responsible for its repellent powers: coumarin and phytol.

Coumarin was the chemical that made Avon’s skin product, Skin So Soft, an accidental hit as a repellent.

The Smithsonian article noted Avon now makes repellents, but without coumarin, because it’s not registered as a repellent with the Environmental Protection Agency.

The research was fun, Cantrell said and he chuckled at learning the findings are sweeping indigenous social media.

“That’s the beauty of this study,” he said. “There is a chemical basis to why this plant was used traditionally.”

alexandra.paul@freepress.mb.ca