We’re right in the deep heart of gardening season here in the East Kootenay. But coinciding with that is gardening season’s dark side — weed season. And the battle against invasive or noxious weeds is ongoing, around the region and the province.

“Invasive plants in general are the second leading cause of biodiversity loss in B.C. and worldwide,” said Marty Hafke, Coordinator of the East Kootenay Invasive Plant Council.
Spotted knapweed, for example, is one of the most aggressive weeds, and one that most people will be familiar with.

“Knapweed has these amazing attributes, from a biological perspective, that make it a real threat to native species,” Hafke said. “It will really take over habitat and displace our native vegetation.

“It will really move in. It secretes a toxin from its roots so that nothing will grow next to it. The seeds can be viable in the soil for up to 100 years. That one seed could be in the soil for decades before a new knapweed plant grows, and these plants can drop up to 3,000 seeds. It’s got a really bitter taste, so that not many animals will eat it.

“All of these characteristics give it a competitive advantage over native vegetation.”

The EKIPC has been doing weed control throughout the season, using “an integrated pest management approach,” including herbicide application, handpulling and bio-control.

“The herbicides they’re using are extremely high tech these days,” Hafke said. “They’re extremely low risk, used in tiny amounts, and tailored specifically to work on the knapweed plant and still leave the native grasses and vegetation to continue growing afterwards.”

There are hand-pulling crews working throughout the region as well, in sensitive areas where herbicides can’t be applied — such as schoolyards, or next to a creek.

But to seek out, treat and control every weed population across the province by human means is, of course, prohibitive. “Really, nobody has those resources available,” Hafke said. “So the other approach that’s being used is bio-control.”

The process of bio-control involves introducing the weed’s “predator” into the local weed population.

“A lot of these plants are from other countries — knapweed is from Eurasia, for example,” Hafke said. “When these plants were introduced, they usually showed up as a seed. But all those things that would keep that plant in check in its native country — funguses, diseases, bugs, weevils — don’t show up with the seed.”

Different bio-control agents include weevils, flies, “lots of different bugs,” said Hafke. “They feed on different parts of the plant — some of them on the inside of the stem, or the roots, or the seeds, or they’ll feed directly on the leaves. They’ll lay their eggs on the plant, and when the larvae start to grow they’ll feed on the inside of the plant.”

Bio-control introduces — very cautiously — the plants’ original predators into Canada.

“People will go back to the plant’s native country, look at all the things that are feeding on it, collect these, and bring them back to Canada — under very strict quarantine,” Hafke said. “They then go through a whole series of tests with each of these little critters to see if they feed on any native vegetation. If they can survive on anything native, they can’t be released in Canada.

“You can imagine the problem that would be created if you brought this little bug over to eat knapweed, and it decided it likes canola.”

There have been a number of bio-control agents — as many as a dozen, Hafke says — released in B.C., including in the East Kootenay. “Once you release enough of these they become part of the environment, they keep the weed population in check. They’ll never eliminate it, but they’ll reduce its competitiveness so it won’t be as invasive.”

Hafke says follow-up surveys conducted this year shows that bio-control is having a positive effect. “We were able to find these critters in the plants, and noticed that the plants are visibly stunted, producing less seed, and just not as (prolific).”

Hafke says a “shining example of local bio-control is the agent that we’ve released on houndtongue — a weevil. These weevils will move into a population, knock it down, then fly off to find the next population and eat that one. As a result, we no longer have to use hand-pulling or herbicide to control it.”

Hafke wanted to add that motorists driving around the East Kootenay this summer are likely to see crews out battling the invasive ones. “They’ve been working really hard,” he said. “Give them a honk if you’re driving by.”

The EKIPC will conduct a summer field tour on September 16. Interested members of the public can come out, meet some of the board members, and check out first hand what the Council is up to, including their work with bio-control. For more information on the field tour, check out www.ekipc.com, or call 1-888-553-5472.