A new weapon in the fight against phragmites

Published: March 18, 2020

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You probably wouldn’t recognize it if it circled your porch light, but a mousy brown moth from Switzerland could be cottagers’ new ally in the fight against the invasive European common reed, Phragmites australis.

In Europe, where the the white-mantled wainscot (Archanara neurica, in scientific lingo) makes its home, its larvae weaken phragmites by boring into stems and eating them from the inside. Scientists are hoping the moth will have a similar taste for Ontario’s invasive phragmites. This summer, they’ll field-test the insect at 28 sites across province. Researchers will gauge its activity, the damage it does to target plants, and whether there’s “spillover” feeding on native species of the reed.

“We’re hoping it will be one more tool in the toolbox for phragmites management,” says Rob Bourchier, an Agriculture and Agri-Food Canada researcher who works with beneficial insects. He said the moth was selected based on its ability to attack invasive phragmites, with little or no impact on other plants.

A second moth—the twin-spotted wainscot—also has potential to control phragmites, but scientists are still trying to raise it in captivity. “We’re just at the point now where we’re figuring out how to rear them on an artificial diet,” Bourchier says. Finding the right insect, testing its effectiveness and getting it successfully transplanted into a new home is painstaking science, he adds. No wonder only about 30 per cent of biocontrols scientists try have a significant impact on the target species. Still, if this imported moths succeeds, they’ll be “another stress on the plant,” Bourchier says, possibly helping cottagers, conservation groups and governments bring it under control.

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