LETHBRIDGE – Eva Pavlik picks up a big, fat worm and lets it crawl across the palm of her hand.
“It feels nice. It would make a good pet,” she tells visitors to Agriculture Canada’s research centre in Lethbridge.
The oversized crawling critter is the hawk moth larvae that feeds on leafy spurge, a troublesome weed in interior British Columbia rangelands and the Alberta foothills. While it looks menacing, this oversized insect does not survive well in Canadian conditions so its effectiveness is not as great as other imported weevils and wasps.
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“They look like they do a lot of damage but they are sporadic. They certainly aren’t doing as well as little flea beetles,” said entomologist Rose De Clerck-Floate.
She and colleague Rob Bourchie are the only federal researchers working on insects to control noxious weeds in Canada.
The successes with biocontrol have been dramatic since armies of insects were introduced in the battle against invasive plant species.
Often, the smallest of the beetles and weevils are most effective.
De Clerck-Floate is especially proud of work done on houndstongue in B.C.’s East Kootenays.
A large, leafy biennial, houndstongue was choking out valuable forages in that province. It is toxic to livestock and leaves burrs on animals.
Since 1997 Lethbridge scientists have successfully established the Mogulones cruciger, a beetle that destroys houndstongue roots.
“Within two years not only was it establishing everywhere that we put it, but it also had a severe impact on the houndstongue patch we put it in,” she said.
Initial work was so successful that East Kootenay ranchers asked for mass production of the insect and an unusual approach was taken beyond laboratory multiplication.
The weed was grown as a crop in Creston and Lethbridge. It received large doses of fertilizer and was well tended to encourage more insects to feed and grow on the plants. Harvesting was done with a shop vacuum cleaner and about 80,000 weevils were collected for release. Most were provided to B.C. ranchers who helped pay for the project.
The project finished this year and an economic analysis is under way.
Dalmatian toadflax is another noxious weed. With characteristic yellow flowers growing up the stem like a garden variety snapdragon, it is found on rangelands, roadsides and disturbed areas. It escaped as a garden plant after being introduced from Europe in the late 1880s. It is a perennial and prolific seed producer.
Shiny black, slender weevils about three to four millimetres long were released.
Out of four European insects tested for use against toadflax, the weevil was the most effective. It tunnels into the stems and prevents flowering and eventually kills the plant.
The adult weevils overwinter in the stems and while they have survived in B.C., they have been less successful in southern Alberta.
De Clerck-Floate suspects the fluctuating effects of Chinook temperatures may impact its survival.
The Lethbridge program of classical biocontrol in conjunction with the B.C. government has researched and released about 70 predator insects on 21 weed species.
Classical biocontrol involves importing insects from a plant’s home country. It is self sustaining control with little stress to the environment. It also addresses the problem of weeds showing resistance to chemicals.
“Some biocontrol agents have to be reapplied over time but that is not the case for classical biocontrol,” De Clerck-Floate said.
Once researchers release a number of insects into an infested area, this can be used as a nursery site where they can collect more for other trouble spots. No further imports are needed.
“When you find these species that are native to Europe they are not in large numbers at all because they have a whole host of things that feed on them to prevent these things from getting out of control,” she said.
The goal is to reduce the plants to a low level.
“You never totally get rid of the weed,” she said.
Some studies have sprung up to look at the genetics of invasive species to see if they are more vigorous in a foreign environment.
