LDD Moth (Lymantria dispar dispar) (also known as gypsy moth)

Please note

We are transitioning away from the use of “gypsy moth” and will be using the acronym for the scientific name “LDD” going forward.



LDD moths (Lymantria dispar dispar) were originally imported to Boston from Europe as a potential silk producer. Unfortunately, they escaped and have been in Ontario for approximately 60 years. The first major outbreak in Ontario was in 1985.

Caterpillars start to emerge from egg masses in mid-to-late May and will spend about 40 days eating all the leaves or needles that they can consume.

LDD caterpillars prefer to eat oak but will eat many other species such as maple, poplar, cherry, willow, birch and spruce.

Each caterpillar will eat about one square metre of leaf material before cocooning for 10 to 14 days in mid-June to early July.

Adult moths emerge from cocoons in late June to early July to focus solely on breeding and egg laying. They don’t eat at all during this stage and live for approximately two weeks.

LDD females usually lay between 100 to 1,000 eggs.

They don’t create ‘tents’ like some other species such as fall webworm or eastern tent caterpillar.

Unlike the devastation caused by emerald ash borer (EAB), LDD moth outbreaks rarely cause damage to forests on a large scale.

For more information on the history, dispersal and management of LDD, view this video.

Frequently Asked Questions

Will LDD moths kill my trees?

Healthy trees can typically survive three to five years of heavy moth feeding. A healthy tree will usually be able to regrow their leaves later in the season. However, if the trees are stressed due to drought, disease, fungi or other insects, this loss of leaves can deplete the tree’s energy reserves and eventually result in death. Unfortunately, conifer trees (though not the moth’s favourite meal) can die after only one year of very heavy feeding.

Does anything eat the LDD moth?

There are over 40 native species in Canada that will eat LDD. Some of the more common bird species include blue jays and orioles (who eat caterpillars), and chickadees (which feed on the egg masses). Mice, chipmunks, skunks, voles and other small mammals will also eat the pupae or caterpillars.

What else helps keep LDD in check? 

Besides wildlife that eat the LDD, there are some other natural control methods including both a virus and fungus. The nuclear polyhedrosis virus (NPV) infects the caterpillars, causing them to die and continues to spread through contact between caterpillars. It can also be spread through the feces of birds that eat dead or dying caterpillars. The effectiveness of the virus is dependent on high caterpillar density. Interestingly, when caterpillars die due to the NPV they hang in an upside down “v” shape, as seen below. The fungus Entomophaga maimaiga overwinters in soil and infects the caterpillars, resulting in their death. It needs cool, wet weather to persist and be effective. These natural controls are part of why the population declines after a few years.

Dead caterpillar due to NPV                          Dead caterpillar due to fungus

How long will a heavy infestation last?

These outbreaks occur every 5-10 years and usually last between two and four seasons. Although much worse this year, the current outbreak is in its third year for much of the province. It is difficult to say definitively, we are hopeful that we see populations decline either later this year or next year. Outbreaks generally collapse due to the combined effects of natural controls: a fungus (Entomophaga maimaiga), a virus (Ld-Nucleopolyhedral virus), and parasitic wasps and flies. The effectiveness of these natural enemies is dependent on weather conditions and the size of LDD moth populations. These cyclical population changes (peaks and collapses) are the reason this species is considered naturalized in Ontario.

What can I do on my property?

Please note: the hairs on LDD moth caterpillars and in egg masses can cause irritation or allergic reactions in some people. Consider using gloves and other protective wear whenever contact is possible.

There are several ways that you can try to help a tree affected by this moth. Usually a combination of these methods works best. You won’t get rid of all the caterpillars, but you can reduce the amount of damage they cause. If there are a few trees on your property that you’re concerned about you can concentrate your efforts on them. If you have a larger woodlot some damage to a few trees is not likely to have a big effect on the forest in the long run.

If you’re worried about the trees on your property you can try the methods listed below or consult a local tree service company.

Action Description Time of Year
Keeping your tree healthy This can mean watering in dry periods, adding mulch to the soil around its base and making sure its root zone is clear of heavy objects or things preventing rain from getting into the soil. Year-round
Egg mass scraping

Until the tiny caterpillars start emerging in May, the oval-shaped, tan-coloured egg masses can be scraped off trees and other surfaces into a container. Fill the container with soapy water, and make sure you stir the egg masses and break them up if possible. Let them sit for two days in a sealed container to kill the eggs and then put them in the garbage. Scraping egg masses onto the ground will not kill them.

LDD moth egg masses can be found on almost any surface, including the side of your house.

View this video for more information.

August – early May
Spraying Btk

Btk (Bacillus thuringiensis kurstaki) is a biopesticide that can kill moths in the caterpillar stage when sprayed on the leaves of affected trees. The caterpillar needs to eat the bacteria off the leaf to be killed. Various Btk products are publicly available, however it should be applied by a registered pesticide applicator. This can be done through ground sprays or aerial sprays for larger forested areas. Consult a local tree service company for ground spray options and research for aerial spray options well in advance of the spring season.

Note: Pesticides of any kind should only be used with the greatest caution. Always make sure to carefully read the label and follow instructions for the proper timing and dosage of application. Visit Health Canada to read about the safety of Btk. This spraying can be done for individual trees or for large scale infestations.

Planning: winter before you want to spray

Spraying: May – June

Trunk wrapping

When the caterpillars are present wrap a wide strip of burlap around the trunk, tie it around the middle with string and then fold down the top to create a sort of pocket. Caterpillars will gather there for shelter during the day and they can be routinely caught and disposed of.

View this video for more information.

May – July
Hand picking caterpillars and pupa Collect caterpillars and pupa from trees or other surfaces into soapy water and make sure the solution is well mixed. And then discard them in the garbage. Wear gloves to ensure your skin is not irritated by the caterpillar hairs. May- July
Set out pheromone traps Pheromone traps can be used to attract and trap adult male LDD moths to stop them from mating with females. Although this is generally used in monitoring LDD moth populations, it can reduce egg mass loading in small areas. July – August

Gypsy moth egg masses can be found on almost any surface, including the side of your house.

LDD moth egg masses can be found on almost any surface, including the side of your house.

When do the different life stages occur? 

This can be variable based on weather conditions and location; however, general timing for life stages are:

Why are the caterpillars found on everything and not just in my trees?

When a population boom occurs. LDD caterpillars often eat themselves out of house and home. Meaning they have eaten all the leaves on their host trees. When this happens, they search for more food by crawling around or dropping down on silk lines and the wind blows them onto something else nearby. When they search for food they are not always successful and this is when they end up on the house, the car, us, or anything else really. Windy conditions can assist in blowing them out of a tree canopy and onto anything that’s nearby. This in part is why the trunk wrapping collection method works. There are caterpillars climbing from below in search of new leaves to feast on, and some above who often come down the branches and trunk seeking shelter in the heat of the day.

Are there any tree injections available to protect my trees?

There is a product TreeAzin which is manufactured by Bioforest. It is a systemic insecticide which is injected into a tree which can provide protection for select trees to LDD moth. When used for LDD moth it can severely decrease the amount of defoliation on a treated tree. These treatments must be done by a qualified professional with special equipment, can be very costly, and require holes to be drilled into the base of each tree. It must be done pre-emptive to the caterpillar outbreak and therefore takes some foresight to be effective as it targets the first few early life stages of the caterpillar. Click here for more information from Bioforest, and here for their listed service providers.

What is CVC doing?

There are many invasive species in our watershed and we’re currently focusing our efforts on the ones that have the potential to cause the most damage to our ecosystems. For this and other reasons we’re not actively managing LDD moth on our properties at this time.
However, we aretaking the following actions to prioritize our efforts in managing invasive species:

  • Developing an Integrated Pest Management framework based on the latest research which will include a LDD moth monitoring program for our properties starting in winter 2021. This work will be used to determine where prioritized on the ground actions will occur to ensure CVC is being ecologically and fiscally responsible.
  • Working with our partners to increase collaboration and formalization of watershed initiatives.
CVC was pleased to provide, in partnership with TRCA, a free information webinar on June 8 on the LDD moth (European gypsy moth). Webinar participants learned about the LDD moth life cycle, how to identify them and what actions you can take to minimize their impact to trees. Access a recording of the webinar here

CVC is happy to provide information and education about management techniques, as described above. If you have questions, please contact us at invasivespecies@cvc.ca

For further information on LDD Moth, visit:

COVID-19 related service changes
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