The Gypsy moth is a forest pest and their caterpillars eat the leaves of a wide variety of trees. High populations of gypsy moth result in tree defoliation with significant potential impacts on tree and forest health. A large increase in gypsy moth was seen across much of southern Ontario in 2020.
The province does not carry out insect control programs on private land. To support landowners in the management of gypsy moths, the Ministry of Natural Resources and Forestry (MNRF) and its partners have developed fact sheets that provide information and outline best management practices. MNRF also conducts aerial surveys to delineate the area and severity of the gypsy moth outbreak. Previous years' survey results and a map of projected gypsy moth defoliation can be found on the Ministries website. To complete your own egg mass survey on your property, you can request the Modified Kaladar Plot (MKP) protocols by emailing info.mnrfscience@ontario.ca.
We all need to work together to best control this pest.
| The Gypsy Moth Life Cycle |
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To manage the spread of the gypsy moth, it is important to know its life cycle. The caterpillars of the gypsy moth are dark coloured and hairy, characterized by five blue dot pairs and six read dot pairs on their back. They go through 4-5 "molting" events in which they shed their skin and get bigger. The four main stages of the gypsy moth life cycle are larva/caterpillar, pupa, adult moths, and egg masses.
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| What can homeowners do to control gypsy moths? |
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Homeowners are encouraged to monitor their hardwood trees like oaks, maples, beech, and walnut for the presence of gypsy moth caterpillars.
| August to mid-April |
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Physically remove and destroy egg masses. This is one of the best ways to reduce infestation - every egg mass removed will reduce the population by several thousand!
Supplies
- A flat object such as a butter knife of plastic paint scraper
- Catchment container or bag to collect the egg masses
- Bucket of soapy water; dish soap works well
Instructions
- Place your catchment container below the egg mass
- 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
- Empty the contents of your catchment container or bag into a bucket of soapy water
- Leave the eggs sitting in the bucket for 48 hours, then dispose of the contents.
Do not drop them on the ground or put them in your composter as the caterpillars will still emerge
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| Mid-April to mid-May |
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Apply biological pesticide to early stage caterpillars. Btk (Bacillus thuringiensis kurstaki) is available for purchase from local hardware stores. This biopesticide can be applied by a registered pesticide application company or by homeowners who have carefully read application instructions. Btk is a product that affects the digestive system of caterpillars.
Health Canada’s Pest Management Regulatory Agency (PMRA) is responsible for the registration and regulation of pesticides in Canada. Staff at the PMRA are responsible for administering the Pest Control Products Act (PCPA) on behalf of the Minister of Health. Registration under the PCPA requires a thorough scientific evaluation to determine that new pesticides are acceptable for a specific use and that registered pesticides remain acceptable for use once on the market. If Canadians choose to use pesticides, they can only use a pesticide registered by the federal government for the pests and treatment areas listed on the label, and use them according to the label directions. The product label of a pesticide contains legally binding use directions, the contravention of which is an offence under the PCPA. Click here for more information on pesticide regulation in Canada.
Residents are discouraged from hiring community members to treat their trees with any pest control product. Provincial regulations require licenced and insured pesticide exterminators to treat private property. A Pesticide exterminator licence is required to apply pesticides commercially on any property that the applicator does not own or farm.
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| Mid-May to June |
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Attach burlap bands to your trees. Caterpillars tends to feed at night, and climb down the tree to shelter from the heat during the day. This will help reduce the number of caterpillars in your tree.
Supplies
- Burlap cloth
- Twine or rope
- Bucket of soapy water, dish soap works well
Instructions
- Wrap and secure a piece of burlap cloth around the trunk of the tree
- Tie twine or rope around the centre of slightly below the centre of the burlap
- 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
- Check the trap by lifting the overhanging burlap cloth every afternoon and collect any hiding caterpillars
- Put them into a bucket of soapy water for a few days, then dispose of the contents
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| June to mid-July |
| Remove pupae by hand and discard by disposing in a soap and water mixture or burn them. |
| July to August |
| Install pheromone traps in trees to lure and trap male moths to prevent them from mating with female moths. You may also use burlap bands technique used from mid-May to June during this time to collect female moths which are unable to fly and will climb up the tree to lay their eggs. Consult with your local nursery or hardware store for information on the proper use of these bands/traps. |
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| Frequently Asked Questions |
| 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. |
| Are there any control factors of the gypsy moth? |
| Natural control factors of the gypsy moth include predators such as wasps, flies, beetles, ants, spiders, chickadees, blue jays, robins, and nuthatches. Animals such as chipmunks, squirrels, and raccoons will also prey on the caterpillar.
The gypsy moth is susceptible to several naturally occurring diseases caused by bacteria, fungi, and viruses. 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.
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| Gypsy moth history in Ontario |
| 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.
There are four (4) stages of the gypsy moth:
- 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.
- 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.
- 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.
- 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.
Area-wide outbreaks occur every 7 to 10 years. See the Province of Ontario site for more information about the gypsy moth.
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| Where can I learn more? |
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