European Gypsy Moth

Gypsy moth caterpillarThe European Gypsy Moth is a non-native defoliating insect that feeds on a variety of tree species found in southern Ontario. In Brantford and surrounding areas, the European gypsy moth can be problematic in forested areas with oak dominant communities such as Mohawk Park.

Accidentally introduced in North America from Europe and Asia in the 1860s, the European gypsy moth has thrived with limited predators and can be destructive to local ecosystems. The moth is of concern because during the larva stage of the insect, the caterpillar eats the leaves of trees, defoliating them which in turn may make them more susceptible to disease and damage from other insects.

European Gypsy Moth - DeforestationAlthough the caterpillars feed on a wide range of hardwood and evergreen trees, they show a preference for certain species such as poplar, birch and oak trees. Every 8-12 years when conditions are suitable, significant increases in populations of gypsy moths occur. These outbreaks can cause large holes in the leaf surfaces or completely defoliate trees and shrubs in large areas. Continued defoliation of trees can lead to their decline and eventual death.

The last outbreak of European gypsy moth in Mohawk Park occurred in 2007. An increase in the population in 2020 has resulted in many trees in Mohawk Park losing their leaves.

Pest management

European Gypsy Moth - Traps

Gypsy moth outbreaks may appear suddenly and may continue for several years in any one location. Natural control factors such as disease, parasites, and predators eventually combine to cause a collapse of these outbreaks. Consecutive years of gypsy moth infestation can cause severe defoliation which can lead to tree mortality. Intervention may be required to control continued outbreak levels of gypsy moth in areas with trees that are at risk of mortality if no action is taken. Eradication of the gypsy moth is not a realistic management objective since it is well established throughout North America. Several strategies to address the pest population may be necessary. Strategies that are the least harmful to the environment are initiated first. Control measures include the removal of caterpillars, burlap banding, insecticide application, installation of pheromone traps, removal of egg masses (where possible), and in some cases biological controls.

City control measures

The City of Brantford is not spraying for European Gypsy Moths at this time. Control measures including removal of caterpillars, burlap banding, the installation of pheromone traps, and the removal of egg masses are being undertaken in Mohawk Park and in other select areas with mature hardwood tree species where outbreaks have been noted. In the late summer, egg mass surveys will be undertaken to assist with anticipating projected 2022 gypsy moth populations, and whether spraying insecticides, biological control measures should be considered as part of an overall management strategy in subsequent years.

European Gypsy Moth Trap

A pheromone trap hanging in a tree. These traps release a chemical to attract male gypsy moths where they’re trapped before they can mate with the female moths (and produce the next generation of caterpillars). Look for these traps in Mohawk Park this year.

European Gypsy Moth Burlap Covered

Burlap banding around the trunk traps caterpillars seeking shelter from heat and predators and female moths.

Captured caterpillars and moths are placed in soapy water for a day or two before being disposed of. Residents can assist in caring for their own trees by following the same pest management techniques at home.

June to July-Hand pick caterpillars
Handpicking caterpillars is still one of the most effective ways to help control European Gypsy Moths on small newly planted trees, shrubs, and plants. If possible, you can also gently shake the tree, so caterpillars fall from the 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. What to look for - The caterpillars of the gypsy moth are dark and hairy. They have five blue dot pairs and six red dot pairs on their back. They go through 4 to 5 "molting" events where they shed their skin and each time, they get bigger.
April to August-Burlap banding

Once European Gypsy Moth 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. Reduce the number of larvae on the trees in your yard by trapping them.

European Gypsy Moth Burlap Band

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 2 to 3 days and then dispose of the contents

Click for detailed instructions for burlap banding.

July to August-European Gypsy Moth trap

Step-by-Step Instructions

  1. You can purchase the traps at various retail stores or online throughout your area
  2. Put the traps out when the moths are active after coming out of their pupa stage of growth. Only male moths are attracted to the traps.
  3. Homemade traps can be created with various designs found on websites. The traps have bait inside their lid that smells like female European Gypsy Moth pheromone for attracting males.
  4. Once captured, put the moths in a container of soapy water and leave them for 2 to 3 days, then dispose of the contents.
August to April-Egg mass removal

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 2 to 3 days, then dispose of the contents. Egg masses can be located high up in trees. Care needs to be taken if trying to access anything aloft, especially if using ladders. Some private tree care companies can be hired to provide this service at heights.

Frequently asked questions

What kinds of trees are most affected by the European Gypsy Moth caterpillar?
European Gypsy Moths prefer the leaves of deciduous hardwood trees like maple, elm and 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. European Gypsy Moths don't appear to like ashes, sycamores, butternuts, black walnuts and dogwoods. 
How much damage can European 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. Most of the hardwood trees can produce a new set of leaves if they have been completely defoliated. But this puts stress on the tree as it uses valuable resources. It is especially stressful if they are trying to do so in a period of hot, dry weather. Fortunately, hardwoods rarely die after defoliation. The best thing you can do is to try to keep your trees as healthy as possible to begin with. If you can, water your trees in those hot, dry periods. 
Does the European Gypsy Moth have any natural enemies?
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 European Gypsy Moth is a parasite of the egg. It is now commonly found wherever European Gypsy Moths are and has become an important natural control. Also, the European Gypsy Moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. The virus and bacteria escalate when populations peak. The European 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.
What can residents do?
Property owners are responsible for managing trees (and pests) on their property. You are encouraged to monitor trees on your property - look for and remove egg masses in fall and winter, caterpillars in spring, and moths in July and August - and take action. Control measures are often not complicated and easily be undertaken by homeowners. For instructions see the Pest Management section above.
Do European Gypsy Moths cause rashes?
Direct skin contact with gypsy moth caterpillar hairs can result in a rash and/or skin irritation. The hairs of the caterpillars contain histamine which some people are allergic to. Not everyone will have a reaction if coming in contact with the caterpillar, but it is possible and is a known adverse effect. As a precaution, cover up, wear gloves and long sleeves and avoid touching the caterpillars altogether. If you do experience any sort of reaction, please contact your family care physician for medical advice.

Lifecycle

The gypsy moth’s lifecycle is important in managing its impact. There are four main stages of the gypsy moth lifecycle:

Gypsy Moth Lifecycle

  1. Egg
    • Late August to early May
    • Stage lasts eight months
    • Dormant, over-wintering stage
    • Egg masses range in size from 2-8 cm long and can contain between 100-1000 eggs

      European Gypsy Moth - Eggs European Gypsy Moth - Eggs

      There are a few simple things you can do to remove gypsy moth egg masses
      • Remove egg masses as you see them, before hatching occurs in the spring.
      • Gently scrape off the egg masses with a dull knife or tool into soapy water. You can also use your vacuum.
      • Keep collected egg masses in soapy water for a few days prior to discarding them into the garbage.
      • If the eggs fall on the ground, crush them with the sole of your shoe.

        Gypsy egg masses removal Gypsy egg masses removal
  2. Caterpillar
    • Early May to mid-July
    • Stage lasts 40 days
    • Tree-damaging stage
    • A single caterpillar can eat an average of one square meter of foliage. They continue to feed, moult, and feed until they are about six to seven centimetres long. Once they’ve finished feeding, they seek shelter to cocoon

      European Gypsy Moth - Caterpillar
  3. Cocoon
    • Mid-July to early August
    • Stage lasts 10 to 14 days
    • Transformation stage
    • After the adult moth emerges, it leaves the empty cocoon behind. The female cocoon is larger than the male cocoon.

      European Gypsy Moth - Cocoon
  4. Moth
    • Late July to mid and late August
    • Stage lasts 10 days
    • Reproductive stage

      European Gypsy Moth - Moth European Gypsy Moth - Moth European Gypsy Moth - Moth

An adult gypsy moth’s only function is to reproduce. Unlike other species of butterflies and moths, adult gypsy moths do not eat anything. The female is larger than the male and is cream coloured. The female moths cannot fly. Instead, she uses pheromones to attract male moths. Male moths are smaller and brown in colour.

Resources: https://www.ontario.ca/page/gypsy-moth