Ottawa's tent caterpillar outbreak may be just the beginning, forester warns

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Individually, they’re beautiful: all furry gold and black and iridescent turquoise.

But when they come by the hundreds, thousands even — in your drink, in your hair, smeared across the sidewalk, smeared across your windshield — well that’s something else entirely.

Spring 2017 has seen an explosion in the population forest tent caterpillars, not just in the National Capital Region, but across Ontario and Quebec. And if you think it’s bad now, this could be just the beginning.

“What we’re seeing is the early stages of what could be a couple of years of outbreak,” said Jason Pollard, a forester with the City of Ottawa. “It’s something that happening provincially. Typically with this bug we’re looking at cycles of every 10 or 15 years and then we’re in it for two, sometimes three years, maybe even longer.”

Barrhaven seems to be Ground Zero for Ottawa, but foresters are also seeing the caterpillars in large numbers in Stittsville, Kanata and parts of Orléans. The wriggling critters have also overrun parts of Gatineau Park, Chelsea and Wakefield.

Chris Latreille and his girlfriend were walking on the trails near Champlain Lookout in Gatineau Park Sunday and were astounded by the caterpillars, which were “literally raining down on us.”

“It was really crazy,” Latreille said. “It was OK at first, we just saw them on the ground, but as we got deeper into trail there were webs across my face. All over my hands. In my eyes. You look up and you’d see five or six coming down at you. They were coming down like Spiderman!”

Two species of tent caterpillar are found in the Ottawa area. The eastern tent caterpillar can be distinguished by the single, solid white down its back and the triangular silk ‘tents’ it builds in the crooks of fruit trees. The forest tent caterpillar is identified by the dotted white line down its back. It doesn’t spin nests, but rather forms masses of several hundred caterpillars on the trunks of trees.

The caterpillars are voracious eaters, stripping leaves from a variety of trees, including poplar, birch, oak, maple and flowering fruit trees. The good news is the caterpillar is an early feeder, meaning many of the trees will be able to grow a second set of leaves later this spring.

“I live an hour west of Ottawa and they’re all around me. I’ve had them down my back,” said Rob Lee, a biologist and member of the Ottawa Field Naturalist Club who lives near White Lake.

“This won’t go on very long. They’re probably a week or two away from pupating and then they’ll become moths. They aren’t like gypsy moths that strip the trees later in the summer when they can’t recover. It’s a natural thing. It’s part of the forest.”

Pollard said city crews are monitoring the outbreak and will be watching closely next year to see if the outbreak worsens. If that happens, the relatively isolated populations will coalesce to cover the city, he said. Saskatoon has endured the pest for a fourth straight summer with one homeowner posting a skin-crawling video of mounds of caterpillars crunching underfoot.


The caterpillars are harmless to humans but property owners can take steps to limit their spread, Pollard said.

Clumps of caterpillars on a tree can be sprayed off with a garden hose or knocked into a bucket of soapy water. You can also wrap burlap around the trunk the of the tree. The caterpillars will crawl underneath it to take shelter during the midday heat, then the burlap can be removed and disposed of. More information can be found on the city’s website.

In the meantime, take time to appreciate the caterpillar’s beauty, says Lee of the Ottawa Field Naturalists Club.

“If you’ve got small kids, have them look closely. They have beautiful turquoise on them and the eastern tent caterpillar has orange on it too. They’re really pretty things — if you’ve got one or two. If you’ve got thousands of them, you’re not going to be happy.”

bcrawford@postmedia.com

Twitter.com/getBAC

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