Guelph tells residents to be aware of spongy moth this spring

The city of Guelph says you should checking your trees for spongy moth.

The city said they’re an invasive species, previously known as gypsy moth, that feed off of tree leaves and whose caterpillars cause defoliation.

Timea Filer, urban forestry field technologist, said the city recently did a survey and found Guelph’s risk of defoliation is mild compared to other cities.

“Last year, our risk for the populations of spongy moths was still lower than many of the surrounding municipalities that are having a lot more of an impact,” she said.

Filer said through the counts of egg masses, not caterpillars, the city saw another decrease in the spongy moth population this year.

She said we should see isolated pockets of heavy feeding in certain neighbourhoods, while other areas will see less.

Filer said the city doesn’t think any trees will die and if they’re healthy, they’ll recover.

The city said you can identify a spongy moth caterpillar by the red and blue dots on its back.

She said we’ll start to see them hatching eggs by late April and there are multiple ways to manage the invasive species.

Filer said you can scrape moth egg masses off of tree trunks and branches and pick the caterpillars off by hand.

“You can also spray BTK products, which is a naturally occurring bacteria; you can find those in hardware stores. But you have to get those early in the season because it sells out quickly,” she said.

“June through August, you can install sticking bands or burlap around tree trunks, remembering to empty those and clean those off every day.”

She said it’s important to catch the caterpillars while they’re really small to avoid having them spread later in the season.

Filer said it’s also important to wear gloves while picking the caterpillars off by hand because they can cause irritations or allergies for some people.

Filer said these are tactics or techniques that people can do on small-scale properties to manage the spongy moth population and they are not meant for larger properties.

She said the most important thing residents can learn from managing spongy moths is the care for trees and understanding the things that impact them.

“While the city does what we can on city property, we’re not stepping in onto private property to deal with the spongy moth, but that’s where people can help us on the broader scale across the city,” she said.

If you do see spongy moths on trees in Guelph, you can fill out an invasive species report on the city’s website.

1:56 Gypsy Moth caterpillar infestation strips trees of foliage across Peterborough County