Not far outside of Beaudry Provincial Park, just west of Headingley, Man., experts on invasive plant species are rearing bugs.

One bug, specifically — Galerucella calmariensis — and it has a mission: to defoliate, that is, eat, purple loosestrife, the aggressive, wetland-loving invasive plant originally from Europe that has been called "the beautiful invader."

The plant grows in flower pots and kiddie pools at the site, used as the sole food source for a hefty population of beetles, ready to be transported and deployed to other spots in the province where loosestrife is a problem.

"It's like a beetle factory," said Lisette Ross, head of wetland services for native plant solutions with Ducks Unlimited Canada.

The beetles aren't much to look at: they're "nondescript brown" and around the size of a pencil eraser, Ross said. But as a nod to National Invasive Species Awareness Week, which ended on Friday, you may want to give the bug a pat on the back.

Purple loosestrife was brought to Canada decades ago to be planted in gardens, Ross said. Then the tenacious plant made its way out of gardens and into wetlands, where it has no natural predators and can out-compete native species to grow into dense, mono-cultural stands.

Robert Bourchier, a researcher with Agriculture and Agri-Food Canada, said the density of purple loosestrife has been on the decline in some regions over the past 20 years and some jurisdictions have made strides in managing it.

It's not easy to pinpoint exactly why, and there are multiple methods to combat the plant, but Bourchier said the beetles "definitely … have played a role in that."

"On the broad scale at which the changes in loosestrife density have happened, the most likely explanation, or based on the data that's there … is that the beetles have had a significant impact on loosestrife."

Less work than weeding, more specific than herbicide

In Manitoba, the plant first became an issue in Winnipeg in the 1990s, Ross said, making its way to other parts of the province through drainage basins.

"Because of the way our province drains, it drains through Winnipeg, up sort of through the north part of Winnipeg and into Lake Winnipeg," she said. "Those areas just north of Winnipeg where there's all these drainage connections into the lake have been really susceptible to purple loosestrife flourishing."

There are a number of ways to battle the plant, but biological control — that is, introducing natural predators like beetles — is a good option for a few reasons, said Bourchier.

Manual methods, like pulling or mowing, are labour-intensive and have to be repeated every year. Chemical options like a general herbicide aren't as targeted. Plus, the beetles can move around and find purple loosestrife on their own.

"Those other methods don't work for a sustained control program," Bourchier said.

"There's a role to be played by all the different control methods, but you're looking at the scale of the invasion."

Galerucella calmariensis, AKA the black-margined loosestrife beetle, has been introduced as a biological control for purple loosestrife, which it loves to eat. (Eric Coombs/Oregon Department of Agriculture)

In purple loosestrife's natural habitat in Europe, the plant has plenty of natural predators. But Ross said researchers in the '90s determined the unique traits of Galerucella calmariensis make it a powerful weapon against the plant in Manitoba.

"We probably looked at about three different species of beetles and landed on the Galerucella beetle as the best option for actually controlling it through a biological approach," Ross said.

They're hardier than other natural loosestrife eaters through cold Canadian winters, Ross said, and they reproduce well. What's more, they're extremely picky eaters.

"One of the things you want to be very cautious of in the beginning is making sure there's not other sort of native species that are out there that the beetle might actually like to feed on and perhaps eradicate by accident," she said.

"And the Galerucella beetle is very specific to the purple loosestrife plant, so it worked very well after looking at the different options."

'Great opportunity to partner'

Groups working to control purple loosestrife started releasing the beetle across Canada in the '90s, Bourchier said. In Manitoba, Ross said those efforts began in 1992 and have continued ever since.

Now, researchers can simply collect beetles from one spot in Manitoba with a strong population and transfer them to purple loosestrife problem-spots elsewhere if needed, Ross said. Ducks Unlimited Canada has been working with community groups to teach them how to transplant the beetles themselves where necessary, she added.

"It's a great opportunity to partner, and I think it's a great opportunity share this knowledge and then to allow them to run with it from, you know, this point forward."

The beetles aren't successful everywhere, Bourchier said. Unlike shovels or herbicide, they're living organisms with their own requirements.

But where they are effective, the impact can be dramatic, he said. A 2016 report by the Ontario Invasive Plant Council noted the beetles reduced the biomass of purple loosestrife by up to 90 per cent per growing season in some areas.

Despite success in mitigating it, Bourchier stressed it's important to continue to monitor purple loosestrife, and all invasive species, so the public doesn't forget how problematic they can be.

"It's important to have that historical perspective in the data from the beginning to say, 'Well, no, it really was a problem,'" he said.

"When bio-control works … if it really works well, it works so well that people don't realize it's there."