City action on LDD Moth (European Gypsy Moth)

ByBrad Bradford

The LDD moth (formerly Gypsy Moth) populations have been very concerning this year, not just in Beaches-East York but also around the city. City of Toronto forestry staff are aware of this and I’ve been working closely with them to make sure they are responding to hot-spot areas. We’ve heard especially about Glen Stewart Ravine and areas around Taylor-Massey Creek. 

The City has done aerial spraying in some areas, and stepped up as much as possible early in the spring season to tackle the issue. They are also monitoring defoliation levels closely right now. This will help give us a read of how many eggs are being laid this season and what we need to do to get further ahead of the curve next season. 

Right now the City’s focus is on protecting trees in parks and ravines. Now that the LDD moth has stopped feeding on foliage and will be emerging as moths, Parks will be planning large scale defoliation and egg mass surveys to the areas where we have been receiving calls and to naturalized areas where there are identified hotspots.  

Once those survey results are in, tailored treatment options will be deployed based on the potential damage for next season  as well as the size and scope of the affected area. The plan will also pay special attention to sensitive tree species (like oak) that make up the majority of the canopy in affected areas. 

There are an estimated 11.5 million trees in the City of Toronto so the City can only do so much for private properties. It’s impossible to address issues in every area, so the focus has had to be on hotspots and high-risk parts of the city. 

As with most things in a successful community, we do have to work together. Especially for issues in the natural environment, we have to be very careful to balance treatments which might have other unintended consequences for these beautiful, delicate ecosystems. For example, BTK-based pesticides are very effective and relatively safe to use against gypsy moth but can have an impact on native caterpillars feeding at the same time. Impacts like this need to be taken into account too. 

What can you do to help?

I’ve been sharing information for members of the community to help them better understand how they can help tackle the problem on private trees through my social media and e-newsletter. Lots more information is available online at 

Most of the action to treat LDD moth is taken from May to September. The three main treatments are:

  • Hand picking caterpillars (May to July)
  • Btk Application (May to early June)
  • Burlap Banding (May to September)

More information on how to safely use these treatments is online here. If you see an infestation on public property please report it 311 by phone or email ( with the exact location. You can also refer to the online treatment map here

I also want to take this opportunity to thank the many volunteers, including the Toronto Nature Stewards who have taken the time to help add to the City’s efforts to tackle the moth this year. With every challenge that comes up in the community, it’s always an incredible support for me when I have members of our own neighbourhoods going above and beyond with their energy and support, always so willing to do their part. 

An update from the Toronto Region Conservation Authority (TRCA):

Both TRCA and the City participate in York Region’s Invasive Species Working Group, where LDD is discussed. Since LDD is behaving like a native pest with natural enemies that help control the population, TRCA and other land managers are not overly concerned about long-term impacts to natural areas and so far, we have not observed significant tree mortality. 

We are currently seeing widespread caterpillar morality due to the NPV virus, a fungus, as well as parasitoids and predators.  Most healthy deciduous trees are able to recover from defoliation and are now re-growing their leaves. In terms of hotspots, these areas are identified in the late fall-early winter via egg mass surveys.  TRCA undertook strategic monitoring in areas of Peel and York Regions last year, which indicated a moderate to severe level of infestation for 2021, and this was definitely proven to be true. 

Due to the forecasted severity, TRCA conducted aerial spraying in the high public use areas of 5 of our conservation parks to ensure they remained safe and accessible to the public.  We did not elect to spray large, forested areas because this species has natural controls, as well as the impact that the treatment has on all caterpillars – it does not discriminate and kills all species of butterfly and moth larva.  This can have serious consequences to migrating and breeding birds who rely on caterpillars for food.