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Gypsy Moth


fuzzy caterpillar looking larva

The European Gypsy Moth is a major forest pest concern because the caterpillar, or larva stage of the insect, eats the leaves of trees, defoliating them which makes them more susceptible to disease and damage from other insects, like tent caterpillars. Continued defoliation of trees can lead to their decline and eventual death.  

A single gypsy moth caterpillar can eat an average of one square metre of leaves.

Knowing the gypsy moth’s lifecycle is important to know how to manage its spread. There are four main stages of the gypsy moth lifecycle: larva/caterpillar, pupa, adult moths, egg masses. Scroll down for specific stage-centric methods to capture and remove gypsy moths and limit the pest’s spread.

We all need to work together to best control this pest.

Three images of gypsy moth egg masses including a female laying eggs

What is the City doing?

The City manages invasive pests according to trends, data collection and impact of the pest.

Currently, gypsy moth is isolated to two pockets in London that are now being monitored.

Last fall egg mass surveys were completed on City trees, such as in parks and along boulevards, to provide a data driven approach to managing the pest.

Several locations in the Byron area were identified as experiencing populations outside of acceptable parameters and projected a gypsy moth increase in 2020. These locations were targeted for manual egg mass removal on City trees, combined with education and information for the community.

The City is taking an Integrated Pest Management (IPM) approach. This means we are using different management techniques to address the pest population starting with the least harmful to the environment. At this time, spraying is not part of the IPM.

What can residents do?

Property owners are responsible for managing trees (and pests) on their property. They are encouraged to review their private trees and take action to remove gypsy moths and reduce the risk of infestation as caterpillars grow larger, and later in the summer, turn into moths and begin to breed.

Get to Know the Gypsy Moth and its Life Cycle!

The earlier and more often the pest’s life cycle can be interrupted the more successful we will be in managing the pest.

We are currently in the caterpillar phase.

What to look for: The caterpillars of the gypsy moth are dark colored and hairy. They have five blue dot pairs and six red dot pairs on their back. This is the classic characteristic they exhibit that no other moth or caterpillar has. They go through 4-5 "molting" events where they shed their skin and each time, they get bigger.

Gypsy moth lifecycle infographic. Circle with months around it and methods to remove gypsy moths.

Click on each season below for detailed methods to capture and remove gypsy moths.

To manage gypsy moth, homeowners can:

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  • May to July: Hand Pick Caterpillars

    Handpicking caterpillars is most effective on small newly planted trees, shrubs, and plants infested with gypsy moth. If possible, gently shake the tree so caterpillars fall from leaves. Thoroughly inspect the remaining foliage, branches, and trunk for caterpillars and using gloves, pick them off your tree. Fallen and collected caterpillars should be placed and left to soak in soapy water to destroy them.

    Other positive ways to protect your trees:

    • Attract birds and other creatures that eat these insects by planting attractive flowers, herbs or shrubs in your garden.
    • Keep your trees healthy by watering during times of drought and mulch as this will help them be more resilient to pests and diseases.
  • June – August (Larger caterpillar stage): Burlap Banding

    Once the caterpillars grow to about an inch (2.5 cm) in length by mid-June, they will move down the trunk to seek shelter from predators and heat during the day. Reduce the number of larvae on the trees in your yard by trapping them.

    Required Supplies

    • Burlap cloth
    • Twine or rope
    • Bucket of soapy water. Dish soap works well

    Step-by-Step Instructions

    1. Wrap and secure a piece of burlap cloth around the stem/trunk of your tree
    2. Tie twine or rope around the center or slightly below the center of the burlap
    3. Drape the burlap cloth over the twine or rope so there is an overhang where the
      caterpillars can crawl underneath to seek shelter during the day
    4. Check the trap by lifting the overhanging burlap cloth every afternoon and collect any hiding caterpillars
    5. Put them into a bucket of soapy water for a few days to destroy them

    Man wrapping burlap around tree trunk and tying with string.

    (Photo credit: Pennsylvania Dept of Conservation and Natural Resoures - Forestry - Bugwood.org)

  • July – August (Female Moth stage): Burlap Wrapping

    To Trap Female Moths: Wrap burlap lower on the trunk of the tree to trap the female moth (which are unable to fly) before it crawls up the tree and lays eggs. This is the same method used for the larger caterpillar stage. Once captured, drown the moths in soapy water.

    Gypsy moth - moth stage on tree. Male and female.

    (Photo credit: USDA APHIS PPQ , USDA APHIS PPQ, Bugwood.org)

  • July – August (Male Moth stage): Hang Pheromone Traps

    Hang pheromone traps in trees to attract male moths, which prevents them from mating with female moths and producing eggs. Once captured, drown the moths in soapy water.

    Pheromone trap hung on a tree for adult male gypsy moths that fly.

    (Photo Credit: USDA APHIS PPQ , USDA APHIS PPQ, Bugwood.org)

  • November – late April (Egg stage): Destroy Egg Masses

    Survey your property for egg masses and scrape them off surfaces into soapy water to destroy them.

    Required Supplies

    • A flat object such as a butter knife or plastic paint scraper
    • Catchment container or bag to collect the egg masses
    • Bucket of soapy water. Dish soap works well

    Step-by-Step Instructions

    1. Place your catchment container below the egg mass
    2. Use your scraper tool to remove the egg mass from the surface. Ensure that all eggs
      are scraped. Try not to leave any residual eggs in bark ridges or crevices
    3. Empty the contents of your catchment container or bag into a bucket of soapy water
    4. Leave the eggs sitting in the bucket for a day or two, then dispose of the contents

    Egg masses can be located high up in trees. Take care, especially if using ladders. Some private tree care companies can be hired to provide this service at heights.

Frequently Asked Questions

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  • How much damage can the Gypsy Moth cause to trees?

    Tree damage depends on the degree of infestation, past defoliations, the tree's vulnerability and the environment and can range from light to almost complete defoliation. If the tree has been weakened or stressed by other conditions, and attacked repeatedly in recent years, the defoliation can result in the death of the tree.

  • What kinds of trees are most affected by the Gypsy Moth caterpillar?

    It prefers the leaves of deciduous hardwood trees like maple, elm and particularly, oak. It will also feed on apple, alder, birch, poplar and willow trees. As the caterpillar matures, and population levels increase, it will also begin to attack evergreens such as pine and spruce. Gypsy Moths don't appear to like ashes, sycamores, butternuts, black walnuts and dogwoods.

  • What is the lifecycle of the Gypsy Moth?

    The moths are seen only in mid-summer. They exist only to mate and after the female lays its eggs, moths of both sexes die. They lay their egg masses on the limbs and trunks of trees, on rocks, buildings, vehicles or in other sheltered areas. The masses remain in place all winter and will hatch the following spring from late April to mid-May. Once hatched the caterpillars begin to feed and continue for approximately seven weeks.

    A chart listing egg, larva, pupa, adult, laid out by month of the lifecycle.

  • Are there any natural enemies (control factors) to the Gypsy Moth?

    Yes. Predators include other insects like wasps, flies, beetles, ants and spiders as well as birds such as chickadees, blue jays, robins and nuthatches. Animals such as chipmunks, squirrels and raccoons will also prey on the caterpillar.

    The wasp that targets the gypsy moth is a parasite of the gypsy moth egg. It is now commonly found where ever gypsy moth is and has become an important natural control of the gypsy moth.

    Also, the gypsy moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. The virus and bacteria escalate when gypsy moth populations peak. The gypsy moth virus disease is often referred to as “wilt” because dead caterpillars hang in an inverted “V” from tree trunks or foliage.

    These natural biological controls contribute the most to keeping levels within a normal range and tend to follow 2-3 years after the gypsy moth populations peak.

  • Should property owners consider a commercial insecticide to help control the population?

    During severe infestation an insecticide may be considered a viable option. Homeowners can consider consulting with, and hiring a licensed contractor to apply pesticide sprays or tree injections. Timing of the application and the treatment of the entire canopy is essential to the success of control. You should also be aware that pesticide applications do not produce an instant defense and will not completely eradicate the problem, but can be very effective in reducing the insect population when used appropriately.

  • Why are there still some egg masses on the tree, after the City has been by?

    Our arborists have worked to remove the egg masses from City trees to reduce the population. It is not possible to eliminate this pest completely as it is well established in our region.  Our overall objective is to reduce numbers. We continue to monitor numbers and will take further action if deemed necessary.

  • My family is experiencing rashes that we think come from gypsy moth caterpillars; what should we do about this?

    Some people may experience reaction to any caterpillars’ “hair” or setae, including the gypsy moth. If you are experiencing any sort reaction, please contact your family care physician for medical advice.

  • Why hasn't the City done a broad aerial spray to manage gypsy moths? Will it happen?

    At this time, the City is not considering spraying. We will continue to monitor and perform defoliation studies in late summer to guide plans moving forward.

    In 2009, the City performed an aerial spray of a biological pesticide called Btk for gypsy moth management. It was applied to a few City owned parks and an environmentally significant area, not over private property. These locations were targeted for having high infected oak tree populations, combined with a several year drought in the area, which compounded tree decline and death.

    Other regions or cities may spray if they continue to experience widespread and severe amounts of gypsy moth damage. The City of London’s current status with gypsy moth is that it is isolated to two pockets that are being monitored. With gypsy moths primarily located in a small portion of the City, management must also keep cost prohibitions in mind.

  • Gypsy moth history & background in Canada

    The European Gypsy Moth (Lymantria dispar dispar) is an invasive forest pest that was introduced to North America from Europe in 1869. It was first detected in Ontario in 1969 and has quickly spread across southern Ontario in the 80’s and is now well established regional pest. In Canada, the Canadian Food Inspection Agency (CFIA) is responsible for preventing the introduction and spread of invasive pest species, including gypsy moth.

    In Ontario, gypsy moth populations have peaked in 1985, 1991, and 2002, according to the 2018 Forest Health Conditions Report produced by the Ontario Ministry of Natural Resources and Forestry (OMNRF 2018). The last outbreak in Ontario, in 2008, was much less severe than previous ones. In 2018, gypsy moth was observed feeding alongside populations of fall cankerworm and forest tent caterpillar throughout the southern Ontario region. This made it challenging to determine the primary defoliator.

    Area-wide outbreaks of the pest tend to reoccur on 10 year cycles and remain high for two to three years.

    Gypsy Moth Life Cycle

    There are four (4) stages of the gypsy moth:

    1. Larva or caterpillar appear in May to June and is the only stage that feeds on leaves; as it grows it passes through stages called “instars” where it sheds it’s skin and get a new one and becomes larger.
    2. Pupa develop in a cocoon after feeding is finished around the end of June. Gypsy moth cocoons can be found attached to tree trunks, firewood and trailers and why it is important to not move firewood.
    3. Adult moths appear in late July or August where the male is dark brown to beige and flies. The female moth is white, much larger than the male and cannot fly.
    4. Eggs are laid close to where females pupate. The female will die one day after egg laying. The male moth can live for a week and mate with many females. The female can lay egg masses of 100 to 1,000.

    A provincial report is completed each year, documenting Forest Health Conditions in Ontario. The 2019 report is not complete yet, but images on pages 87 & 88 of the 2018 report (shown below) help put into context where gypsy moth is located in Ontario as a severe threat, and charts the trends over the last few decades.

    chart showing moderate to severe defoliation in Ontario due to gypsy moth, from 1980 to 2018.

    Map showing gypsy moth in ontario. Severe is shown darker shades of red. It is not red in London.

How to Remove Gypsy Moth Egg Masses: Winter Season