Tree-eating spongy moth eases grip on Windsor, but we're not entirely out of the woods

·3 min read
A spongy moth caterpillar is shown on a tree at Windsor's Ojibway Park on June 10, 2022. (Kerri Breen/CBC - image credit)
A spongy moth caterpillar is shown on a tree at Windsor's Ojibway Park on June 10, 2022. (Kerri Breen/CBC - image credit)

Parts of Ontario are being hit hard by the invasive spongy moth — which gobbles up tree foliage — but so far this year, Windsor-Essex is getting a bit of a reprieve.

That's according to Tom Preney, the city's biodiversity coordinator. He hopes it's a sign that the population, which goes in cycles, is on a downswing after several years of heavy infestations.

"In one instance, I was walking down a trail last year and it was raining caterpillar poop out of the trees because there was so many spongy moth in the area, but this year it doesn't seem to be as bad," he said.

That's not to say the species has gone away entirely. Preney didn't have to venture far on the trail at Ojibway Park on Friday afternoon to spot a caterpillar or one of the moth's egg masses.

The species gets its name from its spongy egg masses that appear on trees, he said.

Kerri Breen/CBC
Kerri Breen/CBC

In March, the Entomological Society of Canada and its U.S. counterpart announced that Lymantria dispar would be known by the common name of spongy moth, replacing a moniker that contained an ethnic slur.

The species has also been referred to as the LDD moth.

The eggs usually appear on trees in late April or early May, explained Ryan Statham, a district manager for Davey Tree who is based in Strathroy, Ont.

Then, those destructive caterpillars emerge.

This year, there are heavy populations around Bancroft, Strathroy, Sarnia and along Lake Huron, he said. The city of Toronto is conducting aerial sprays to control the population.

Kerri Breen/CBC
Kerri Breen/CBC

"What we've seen is that the focus of these infestations tends to move all the time," said Statham.

In Windsor-Essex and Chatham-Kent, Statham said the company has been called out to properties that were "loaded with the egg masses" this year.

What can you do?

The spongy moth caterpillar isn't all that picky about its dinner. Its been known to target a wide variety of hardwood trees. In high enough numbers, they can strip a tree of its leaves entirely, Preney said.

A tree can usually sprout fresh foliage, but it's a significant drain on its resources, according to Statham. Depending the tree's health, and with multiple infestations, it could die.

Kerri Breen/CBC
Kerri Breen/CBC

The egg masses themselves, which Statham said can contain up to 1,000 eggs, are easy to scrape off the trunk of a tree.

But there are options after they hatch as well, like wrapping burlap against a tree to prevent the caterpillars from reaching the foliage.

Statham said an arborist can recommend options to tackle the issue. Treatments include the application of insecticides, tree injections and applying sticky bands to the stem of the tree.

The city of Windsor is tracking the presence of the moth. If you see a spongy moth infestation on your property, Preney said you can contact 311 or the Ojibway Nature Centre so they can make a record of it.

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