Ontario’s Trees at Risk from Invasive Species


Although the majority will say that summer 2021 is most welcome after a long winter, made longer by off and on again lock-downs, an added layer, this season, however is the return of the Gypsy Moth.  An invasive species brought to North America in 1860 by a French entomologist who had hoped to cross-breed them with the silkworm, the scientific community has warned that this summer could be a significant year for these foliage-eating caterpillars.

And word on the street is that the Gypsy Moth caterpillar (Lymantria dispar) is not particular about what it eats.

“It really likes oak and birch and aspen,” said Chris MacQuarrie, in the CBC article. “It also eats maple and beech, and it’ll even eat some of the softwood species such as white pine and balsam fir and … Colorado blue spruce…Once it’s done with the trees, it’ll even drop down and feed on understory plants and bushes.”

With the last heavy hit from these populations dating back to the early 2000’s, outbreaks tend to be cyclical and occur every 7 to 10 years.  Under ordinary circumstances, predators and disease do a moderate job of keeping their numbers low, season to season.  MacQuarrie cautions “when the weather’s right, those diseases don’t do such a good job of controlling the caterpillar and they can outbreak,”

There are ways that you can combat these hungry insects, including BTK Caterpillar Killer–a biological insecticide that is available for home use against very young gypsy moth caterpillars, but has been shown to be less effective once they are more grown.  MacQuarrie recommends a burlap banding method against clusters of larger caterpillars.

“Wrap a band of burlap around the tree. As the caterpillars come down from the canopy of the tree during the day, they’ll take shelter underneath the burlap. Folks can come along at night … and pull them out from underneath the burlap and throw them in a bucket of soapy water,”

To learn more about these caterpillars, or advice on how to manage an outbreak, go to Natural Resources Canada also has more information on the caterpillars. For more on the outbreak, you can refer to the Ministry of Natural Resources and Forestry website.

–with files from CBC.ca







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