London

City sees more than 100 complaints about gypsy moth caterpillars in Byron

Residents in Byron have complained the insects are invading their backyards and munching away at their trees.

Staff collecting data on defoliation, egg masses before city considers aerial spraying

Gypsy moth caterpillars have taken over London's Byron neighbourhood, with the city receiving more than 100 calls about the pests. (Sofia Rodriguez/CBC News)

The city of London has received more than 100 calls and emails from people in Byron whose properties have been overtaken by gypsy moth caterpillars. 

Residents of the southwest London neighbourhood have complained the insects are invading their backyards and munching away at their trees.

The city asked residents to reach out to get a better sense of the problem, said manager of urban forestry Jill-Anne Spence.

"We were able to map out where we think the majority of calls are coming from and based on this we sent staff out and verified, in fact, that insect was gypsy moths," she said.

Gyspsy moths are an invasive species that can completely defoliate or strip a tree, causing long-term damage, Spence explained.

"If we're in kind of like a peak boom of gypsy moths, we want to know that. And we heard from a lot of Byron residents that, you know, there were gypsy moths last year, but not as bad as this year, so it sounds like the population is growing," she said.

The city has started working with a consultant to collect data on defoliation and egg masses in the area.

Gypsy moth caterpillars are partial to birch, oak and maple trees. They can completely defoliate or strip a healthy tree, which can lead to long-term damage if it keeps happening year after year. (Sofia Rodriguez/CBC News)

Some tree damage from gypsy moths is expected, Spence said, because the insects have been well-established in southern Ontario for several decades. 

What the city is looking for now is anything that is "out of normal, acceptable parameters." 

"So that's basically looking at egg masses, like how many eggs the moth will lay this fall or late summer," Spence said.

"Based on that data, it'll determine what we can expect the population of gypsy moths will look like next year."

Natural enemy

The last time London faced a large outbreak of gypsy moths was in 2008 and 2009.

Spence said the city tried a few things to curb the population then, including spraying BTK — or bacillus thuringiensis var. kurstaki — a naturally occurring bacteria that targets the gypsy moth caterpillar.

Other strategies included scraping and vacuuming the egg masses, and using pheromone traps to lure the male moths (female gypsy moths don't fly).

"Those are two things that people can do right now that will have a significant impact on the population next year," Spence said.

Once the city has collected enough data on the insects, Spence said they will decide how best to tackle the problem next spring. Any spraying would require helicopters, road closures and coordination with homeowners, she explained.

There is some good news for residents in Byron. Spence said there are three natural predators for the gypsy moth — a virus, a bacteria and a wasp — and there are signs of at least one in the area.

"We've actually seen the virus and it's very symptomatic. The caterpillars actually will die and when they do, they hang upside down in a 'V,' so if you see those types of things out in your yard, that's a good sign that the virus is in our environment," she said.

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