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E-BLAST: Tree Wars: Return of the Gypsy Moth

A year ago, our community here in Don Valley North had to face an additional struggle on top of the COVID-19 pandemic: a European gypsy moth infestation. I’m lucky to have such engaged and proactive residents in my ward. You were the first to observe this infestation, and by reporting it to my office we got City staff on the case straight away.

The City’s Urban Forestry staff had already been responding to sightings of these prolific little moths in the west end. Suddenly, we needed them to head east to Don Valley North and act fast. They have been responding to the infestation on a city-wide basis ever since.

Last summer, my team and I disseminated information on gypsy moths through this E-Blast. We also made an instructional video demonstrating how to remove unhatched egg masses from the trees in your yard. I remember driving up to Lescon Park to film the video with one of my staff, my husband, and my 13 year old grandson, who turned out to be a decent little camera man. You can watch the video below:

Egg mass removal is effective from August to May, before the caterpillars have hatched. Other strategies are needed to beat these bugs the rest of the year. Since filming that video, I’ve made a dedicated page on my website with comprehensive information on how to respond to gypsy moths. It includes a downloadable copy of the City’s informational pamphlet that was sent to homes in affected areas. I encourage you to print and circulate the pamphlet to any neighbour that needs to know what to look out for on their own trees. You can find all of this at my website:

Recently, we have been receiving new calls about this year’s gypsy moth sightings. A few residents have asked why we haven’t been able to get rid of these things completely. Unfortunately, the species is so well-established in North America that eradicating the moths is no longer possible. Instead, we all have a part to play in managing the moths at every part of their life cycle. Let’s review what the City has been doing to manage this year’s infestation and what you can do to help.

At any point in the year, you can report a gypsy moth sighting to City staff to help inform their work for the following season. You can report gypsy moths by calling or emailing 311, or by using the City’s new online reporting tool:

Based on these reports from last year, the City’s contractors removed unhatched egg masses from approximately 1000 trees in Don Valley North over the past several months. To put that into perspective, removing eggs from 1000 trees is equivalent to stopping 1,000,000 caterpillars from hatching.

These 1000 trees were all on City property, whether that be in City parks or on the boulevard in front of your home. It’s important to note that trees located on private property, like your backyard, are the responsibility of the property owner. The City has created its own webpage with comprehensive information about what you can do to deal with gypsy moths on your private trees. They add an important bottom line: if you are facing a serious outbreak on your own property, they recommend you call an arborist to get professional advice and possibly full treatment for your trees.

So what do you need to do right now? Currently, the caterpillars are the things you really want to stop. Having just hatched over the past couple of weeks, they will continue to feast on trees until mid-July when they enter the cocoon phase. These caterpillars eat so much, they can completely defoliate a tree and others around it. Some trees are at a higher risk than others, particularly oak trees. The trees won’t necessarily die, but they become quite vulnerable while they’re defoliated.

If you notice gypsy moth caterpillars on your trees, there are two things you can do. From late May to early June, you can apply a Btk solution to your trees. You can purchase this product at the hardware store, and it won’t harm the tree itself, just the insect. Until July, you can also hand-pick caterpillars from your trees and bushes and place them in a bucket of soapy water to destroy them. This is most effective on smaller trees and shrubs. Be sure to wear gloves while doing this, as we recently learned that the residue left behind by these little pests can cause an itchy skin rash.

Once again, I’m feeling blessed to have such engaged and diligent residents in my ward. It was a resident just like you who reported that the caterpillars can cause skin rashes, which has since been confirmed by a doctor. This has put me on another quest to ensure this important health information is added to our City’s website and literature pieces on gypsy moths.

By doing your part to remove caterpillars from your trees now, and egg masses later in the summer, you can help control the gypsy moth population in our neighbourhoods. I know how bothersome these pests can be, so my team and I will continue to assist you with any questions or concerns you have about gypsy moths. Together, we can reduce the impact of these bugs so that we (and our trees) can enjoy the beautiful spring we’ve been having.


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