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Release the weevils

10/10/2017

The MD of Bonnyville has released thousands of CanadaThistle Stem Mining Weevils into areas throughout the municipality.

Janice Boden, assistant agriculture fieldman for the MD,said this is their attempt to rid natural pathways of the thistle, followingsome resident complaints.

Canada Thistle Stem Mining Weevils are small bugs that onlymine in plants directly related to the Canada Thistle.

This means crops, flower beds, and other vegitation will notbe affected.

Thistles fall under the Alberta Weed Control Act as noxiousplants, with a root system that can extend up to six-metres deep undergroundand over four-metres horizontaly, making it difficult to remove the plant byhand.

The weed’s 1,500 seeds disperse by wind, and can remain inthe soil for up to 20-years.

“We have a lot of environmental areas around the lakes wherewe can’t use chemical or mechanical cultivation to control the weeds. CanadaThistle is one of the weeds that we get lots of calls on,” explained Boden. “Wehad to come up with a way of how we were going to control these weeds.”

The MD decided to conduct a trial using weevils.

The small crafty critters burrow their way into the stems ofthistle weeds and lay eggs. Once the eggs have hatched, the weevils consumeplant tissue, leaving small holes in the weed for disease to enter and attackthe thistle.

“We are doing a trial over by Moose Lake along one of thepathways, which are used as an access by different residents to get to thelake,” said Boden.

The use of weevils to eliminate Canada Thistle has beenapproved in Canada since 1965.

They coninually breed, but don’t have “a populationexplosion.”

The bugs don’t bite, and because they only target thistleweeds, it was the optimal choice for the MD, said Boden.

“One of the things people think is that weevils will eattheir house, that they’re like a termite. They’re not. They eat thistle only,and a couple of close weed relatives to thistle. They won’t get into yourgarden or lawn. They’re going to stay in these thistle patches,” Bodenexplained. “The reason they haven’t caught on really well in Canada is becauseit’s a really slow process.”

Weevils are slow moving bugs. Taking-out a 10-metre patchcan take up to four-years.

“We don’t want this thistle around our lake areas... We’repretty excited about the trial,” said Boden.


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