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European gypsy moth population explodes this year, experts say conditions right

Saturday, August 22nd 2020, 3:45 pm - If you’ve seen white moths on trees with orange looking fluff beneath them on your property, get ready to remove this invasive species. What you’re looking at is the European Gypsy Moth and researchers are asking for your help in getting rid of them.

Have you seen an overwhelming number of white moths on trees this year? You're not imagining it - experts say 2020 has been the perfect storm of conditions for the European gypsy moth.

“Once in a while they kind of explode - all the conditions are right,” said Richard Hamelin, a professor at the department of Forest and Conservation Sciences at the University of British Columbia. “It seems to be a year this year where everything, perfect storm, conditions were right and these moths just went crazy, reproducing -- It's a big year for the moth, but it's not every year.”

Hamelin is talking about the European gypsy moth population in eastern Canada, a population he and his research team hope to keep away from establishing in the west. It is an invasive species first introduced to North America back in the 1960s. It wasn’t until the 1980s that the populations began to establish.

“It was introduced to North America actually by someone who wanted to find a way to make silk. One of the scientists in the United States, as many of these invasive species stories go, thought he had a good idea. He was going to bring in an insect that he thought could be bred to make silk,” said Hamelin. “It escaped from its breeding facilities and then it started spreading. It has spread ever since.”

The damage done by these insects is massive. They feed on the foliage of a variety of trees.


“The larvae feed on trees and on the tree leaves. So it's not the adults that are actually doing the tree. It's actually the caterpillar,” said Hamelin. “They really like oak, for example, their favourite host, but they can feed on just about any deciduous trees that they can think of from maple to beeches. It can even feed on some conifers like white pine for example.”

Caterpillars live the longest, for about a year before they turn into a pupa and metamorphose into a moth. It is in the pupa stage from June to July and the adults begin to emerge from July to August. Female moths are not picky about where they lay their eggs, or egg masses, that can contain hundreds of eggs.

“They're quite conspicuous when you learn how to recognize them on the bark of trees or sometimes on any surface. It could be on the wall of your sheds or even sometimes on trailers and that's how they can move around,” said Hamelin.

The Canadian Food Inspection Agency is asking Canadians for help in recognizing the species and disposing of it properly. A lot of people are going camping this summer and they should be doing a thorough inspection of equipment before heading out.

“Having a look around your equipment, any kind of outdoor furniture you may want to bring with you just to make sure there's no egg masses on them is also a good thing to do before moving on a distance,” said Mireille Marcotte, who is with the plant health surveillance unit of the CFIA.

Also remember to get firewood near your campsite.

“Moving firewood is probably the riskiest thing you can do,” she said. “Most often firewood is made of wood, or it's of trees that have died, and you may not know exactly why the tree has died. There might be pathogens, insects hidden under the bark and then when you bring them to your camping site, near your campfire, you may not burn all of them at once.”

The insects then have time to come out and enter neighbouring trees.

“Then you're starting a new point of infestation,” said Marcotte.


August happens to be tree check month and Canadians are being urged to check trees on their property - not only for the European gypsy moth.

That goes for all invasive species. A list of them can be found on the CFIA’s website.

“August is the time of year where the trees are the most beautiful, the leaves are all out so if there's a problem that's now that signs will start to show. If leaves are falling on the ground now prematurely, if they're turning yellow or brown, if there's cracks on the bark of the trunk, if you see holes in the bark, signs that insects have came out of the wood, then we need to pay more attention and try to find out what's causing those damages,” said Marcotte.


From August to May of the following year, egg masses will be present on all sorts of surfaces.As gross as it sounds - you have to scrape the egg masses into soapy water and keep them soaking for at least 48 hours, then dispose of them.

If it’s earlier in the year, around May to July when the larvae are emerging, some people turn to burlap to protect their trees.

“To prevent the caterpillar from reaching the branches some people put burlap on the trunk of their trees and then you can go daily oh, you're going to love this, cuz you should go and collect those caterpillars that are stuck in the burlap and then destroy them and whichever way you prefer,” said Hamelin.

Municipalities hold their own information seminars for residents to ensure they are educated on the topic of gypsy moths. The City of Mississauga, for example, sent out a flyer to its residents regarding gypsy moth maintenance.

Flyer moth

“The likelihood of eradication or containing any invasive species is way higher if we detect them early so that's how we ask people to check for these invasive species and their neighbourhood and let us know if you see something unusual,” said Marcotte.

Of course if you suspect a new invasive species in your area, you should contact your local CFIA office.

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