Researchers strive for biocontrols to manage invasive weeds

LACOMBE, Alta. — In the war against weeds, one of the best weapons is natural control.

Plants that were introduced from other parts of the world often run out of control because there are no predators to keep them in check. Biocontrol introduces natural enemies to get rid of a targeted weed.

“Biocontrol is not meant to eradicate the weeds. It is just meant to bring it down to a manageable level within the environment,” Karma Tiberg of Agriculture Canada said at the Lethbridge Research Centre.

The controls are often predator insects, but mice, nematodes, fungi and bacteria may be used.

However, because the predators are not native, it may take the Canadian Food Inspection Agency 
10 years to approve the release of a particular agent, she told the Alberta Invasive Species Council annual meeting in Lacombe March 23.

These agents must be cost effective with a low environmental impact. They have to be able to survive in their new range and should die out once the troublesome weeds are gone.

Biocontrol began in the 1930s but took off in the 1950s when scientists started looking at more creative ways to get rid of problem plants. There were fewer regulations at that time.

In 2001, the Lethbridge Research Centre partnered with seven southern Alberta counties and the City of Lethbridge to release agents.

That program was supposed to run for two years, but it continued because of popular demand. In 2016, a partnership with the Alberta Invasive Species Council helped fund research, rear new predators and monitor sites.

Weevils and beetles have been released to attack plants by preventing them from flowering and spreading seeds, defoliation or damaging roots.

Weevils have gone after dalmatian toadflax, and different types of beetles have been released on leafy spurge.

There were 128 new biological releases in 2016 compared to 98 releases in 2015. Most were delivered to control houndstongue, dalmatian toadflax, leafy spurge and spotted diffuse knapweed. The highest demand is for leafy spurge and knapweed agents, said Tiberg.

Funding for biocontrol development is often limited, said consultant Alex McClay.

“If we found a biocontrol for Canada thistle, it would be the Holy Grail and we would have funding for biocontrol forever,” said McClay, owner of McClay Ecoscience.

The predators are collected from their native range and then multiplied and tested to see if they can work in a new environment.

A lot of this work starts in Switzerland and the United Kingdom under contract to Canadian and American sponsors.

Recent work is looking at biological controls for common tansy, a native to Europe that is spreading in Alberta in pastures, roadsides and riparian areas.

“It is taking a while because they have had to reject a lot of the candidate agents that did not fulfill all the requirements,” he said.

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