Lymantria Dispar Dispar (LDD Moth)/Spongy Moth
Spongy moth (also known as Lymantria dispar dispar or LDD moth) is a naturalized invasive insect found throughout southern Ontario that feeds on a variety of tree species such as oak, birch and maple. It is known to have cyclical outbreaks every 7 to 10 years. Spongy moth caterpillars eat leaves causing the trees to lose some or in extreme cases, all of their leaf canopy. However, since the canopy has the ability to regrow as the season progresses, long term effects can be reduced or prevented through management techniques.
Southern Ontario, including Richmond Hill has been experiencing a spongy moth outbreak since 2019. Outbreaks typically last 3 to 4 years. Recent York Region survey results indicate that we are nearing the end of this outbreak and the impacts of spongy moth are expected to be minimal in 2023.
How to identify spongy moth and infestation |
Spongy moth life cycleThe spongy moth has four distinct developmental stages in its life cycle similar to other butterflies and moths.
What does a spongy moth infestation look like?
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Richmond Hill's plan to manage trees on public property |
With the impacts of spongy moth expected to be minimal in 2023, Richmond Hill will not be conducting city-wide management activities, such as egg mass removals. The City will continue to use a number of different methods to minimize damage to trees on public property and help reduce the spread of spongy moth in our community. This includes:
The City will not be conducting aerial spraying to treat spongy moth caterpillars. Aerial spraying is costly, does not reduce the pest’s population over the landscape long term, but aims to reduce defoliation levels. Aerial spraying requires multiple treatments, is only 60 to 80% effective and can still result in leaf loss. It can also affect other moth/butterfly species, which are an important source of food for many birds and other wildlife. In fact, squirrels, chipmunks, raccoons, skunks and more than 15 species of birds and several native insects will all help reduce spongy moth numbers. In addition to wildlife, a naturally occurring fungus (Entomophaga maimaiga) and virus (nucleopolyhedrosis), both harmless to humans, will also contribute to an eventual collapse of spongy moth populations. |
What you can do to protect the trees on your property
Trees on private property are the responsibility of the property owner. You are encouraged to monitor the trees on your property to identify any signs of infection and take action protect your trees.
There are a number of actions you can take to help reduce spongy moth populations. Control methods are closely linked to the LDD moth’s life cycle stage and time of year. To help prevent infestation, water your tree regularly to promote tree health, especially during the hottest days of summer.
Burlap kits will be available for residents to pick up for free (while quantities last) at the Operations Centre (1200 Eglin Mills Rd. E) from 8:30 a.m. to 4:30 p.m., Monday to Friday beginning April 3.
Late August to early May - Egg mass removal |
Watch the How-to Video |
Early May to mid-July - Remove caterpillars using burlap traps |
How to install and monitor burlap traps
Once the trap is set
Burlap bands can be removed in September once the caterpillars have gone into the cocoon stage. Watch the How-to Video |
Other helpful resources
Same insect, new name: The Entomological Society of Canada (ESC) has adopted the new common name of ‘spongy moth’ for Lymantria dispar dispar or LDD moth. Richmond Hill is joining the ESC, York Region and many other government agencies in adopting this new name. Over time, references to LDD moth in City materials will be changed to spongy moth.