Property, Gardens & Trees

Lymantria Dispar Dispar (LDD)

Commitment to Inclusion As part of the City of Hamilton’s commitment to diversity and inclusion, the City has replaced the name gypsy moth with its Latin name, Lymantria dispar dispar (LDD) in it’s communications to help educate residents about the invasive pest while remaining sensitive to the negative connotations associated with its common name.

Notice of second phase of LDD Moth aerial spray - Complete

As part of the City’s aerial spray program to address areas where significant LDD Moth (previously referred to as Gypsy Moth) populations are located in Hamilton, the second of two bio-pesticide applications was scheduled for Tuesday, May 31, 2022, 5 am to 7:30 am and Wednesday, June 1, 2022, 5 am to 7:30 am.

During this time, low flying helicopters will begin applying an organic biological insecticide to wooded properties and residential streets in east and west Hamilton, Ancaster, Dundas and Waterdown, to help manage the infestation on City-owned properties.

Residents may experience minor traffic delays during this time.

Update: The second phase of the spray program was able to be completed in one day instead of two, and an aerial spray is no longer scheduled for Wednesday, June 1, 2022."

Read the full media release

Notice of first phase of LDD Moth aerial spray - May 24, 2022

As part of the City’s aerial spray program to address areas where significant LDD Moth (previously referred to as Gypsy Moth) populations are located in Hamilton, a bio-pesticide applications is scheduled for Tuesday, May 24, 2022 between 5 am and 9 am, weather permitting.

During this time, low flying helicopters will begin applying an organic biological insecticide to wooded properties and residential streets in east and west Hamilton, Ancaster, Dundas and Waterdown, to help manage the infestation on City-owned properties. 

Residents may experience minor traffic delays during this time.

Update: As a result of upcoming rain and higher temperatures, the spray program has been modified so that the first phase of the spray program can be completed in one day instead of two. The first aerial spray will be completed by 9 am on Tuesday, May 24 and a second spray date will be scheduled, dependent on weather and pest emergence, approximately 5 to 10 days after the first aerial spray.

Read the full media release

Public Notice of Pesticide Use for LDD Moth Control – May 15 to June 15, 2022

Between May 15, 2022 and June 15, 2022, the City of Hamilton will be administering an LDD Moth Control Program by applying a bio-pesticide (Foray 48 Biological Insecticide Aqueous Suspension PCP# 24977) will be applied to wooded properties and residential streets in East and West Hamilton, Ancaster, Dundas and Waterdown, to help manage the infestation on city-owned properties.

To see if your property is within the area, add your address into the interactive map below.

The helicopter will be flying at low altitudes, approximately 15 metres above tree tops, between approximately 5 am and 7:30 am on the scheduled spray dates. The exact dates and time for the aerial spray are weather dependent and the City will share up to date details 48 hours prior to each application on this webpage and the City’s Twitter channel. Each treatment area will be sprayed twice, with the second application occurring seven to 10 days after the first application.

View the Safety Data Sheet (SDS) for Btk pesticide English version  |  French version

Residents can request 48 hour advance notice by contacting the Customer Contact Centre 905-546-CITY (2489) or 1-877-446-2424 toll free.

Lymantria Dispar Dispar (LDD Moth) is an invasive forest pest that was introduced accidentally in the United States in 1869. Since then, the LDD moth has expanded its range over much of the eastern United States and Canada. It was first detected in Ontario in 1969 and has quickly spread across southern Ontario. It is now well established throughout southern Ontario and as far north as Sault Ste. Marie.

LDD moth larvae or caterpillars will feed on tree leaves. If the larvae population is high, they can defoliate whole trees and forests in a short amount of time. LDD moth prefer oak trees, but will feed on a variety of hardwood tree species. Under normal circumstances, defoliation caused by LDD moth won’t kill a tree. However, trees can decline to the point of death in some cases when defoliation is coupled with dry hot summers or impacted by other forest pests like Spring or Fall Cankerworm.

Close up of Gypsy Moth Larva
Figure 1: Late instar LDD moth larva

Close up of 3 Gypsy Moths
Figure 2: Female LDD moth laying eggs

LDD moths spend the winter as partially developed larvae in eggs. The eggs hatch in the spring and the young larvae begin feeding by cutting small holes in the surface of leaves. As the larvae develop, they feed on the edge of leaves. Larvae have five pairs of blue and six pairs of red spots along their backs. Feeding is normally completed by early to mid-July.

Pupation occurs in a cocoon which can be found on a variety of surfaces including trees, rocks, houses, boats, trailers, fences, picnic tables, and firewood. In 13 to 17 days, the moths emerge. Both sexes have wings, but only the males can fly. The male moth is dark brown to beige, medium-sized, and is a very erratic flyer. The female is mostly white and has a wingspan between 60 to 70 mm. The female lays eggs in masses of 100 to 1000 on tree trunks, branches, houses, fences, etc. as well as under rocks and forest floor debris. The eggs are covered with fine brown hairs from the female’s abdomen. The egg masses will remain all winter and caterpillars will hatch in the spring, from late April to mid-May.

Gypsy Moth Life Cycle

LDD Moth Treatment Area

 To find out if you live in the treatment area, enter an address or intersection into the search box. If your search result appears in the pink highlighted boundary, you are located in the aerial spray zone.

Once the spray program has been completed this year, the Forestry Section will be conducting follow up surveys of the spray area, as well as areas outside of the spray area to verify that the LDD moth population has decreased below threshold levels. If it has been determined that action thresholds have been reached in other areas, the Forestry Section will address it the following year.

Find more LDD Moth data in our Open Data Portal

How The City is controlling LDD moths

Surveying has been underway since the winter of 2016 with the completion of egg mass surveys. In late 2020 / early 2021 The City had surveys completed to determine egg mass counts in areas that had shown high numbers in previous surveys but were not treated and / or areas where residents and staff noticed increased activities in 2020.  Following a review of this information The City will be considering ground spraying using Bacillus thuringiensis ‘kurstaki’ (Btk), as well as banding of City trees in these areas.

Bacillus thuringiensis ‘kurstaki’ (Btk) is a soil-borne bacteria that is applied to the leaves of affected trees while caterpillars are in their early instar stage (immature). Once ingested, the bacterium disrupts the caterpillars’ digestive system with cessation of eating within 24-48 hours. Within days, caterpillars that have ingested Btk will succumb to its effects. Btk has very low residual qualities in the natural environment. Sunlight and fungi deteriorate the bio-pesticide within 1 to 4 days. Because Btk requires an alkaline environment in the gut in order to be effective, it does not have any detrimental effects to humans, birds, or bees. Btk will affect other caterpillar species (known as non-target species). Due to its low residual and the narrow spray window due to larval development, the non-target impact is expected to be low. Conservative and measured application will be undertaken with the goal of reducing the population below the 2,500 egg masses per hectare. This program is not intended to eradicate the pest entirely.

Members of the public are unlikely to experience any symptoms if inadvertently exposed to Btk spray, and no special precautions are necessary or required. However, individuals who have concerns should take reasonable precautions to avoid exposure during a spray program in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued. They can also reduce exposure by staying indoors with windows and doors shut during the spray period if spraying is taking place in their area, although this is not required by health officials. (Health Canada, 2009)

What homeowners can do to control LDD moths

Homeowners are encouraged to monitor their hardwood trees like oaks, maples, beech and walnut for the presence of larvae. You can help manage LDD moths by follow these techniques:

Handpicking caterpillars is still one of the most effective ways to help control LDD 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 LDD moths are dark and hairy. They have five blue dot pairs and six red dot pairs on their back. They go through 4-5 "molting" events where they shed their skin and each time, they get bigger.

You can apply a product that contains BTK (Bacillus Thuringiensis “kurstaki”)  to foliage at the early stage of caterpillar development when caterpillars just begin feeding. This is usually around mid-May. The pesticide must be ingested by the caterpillar to be effective. 

For small trees and shrubs that you can reach, products like Safer® Brand Caterpillar Killer can be purchased at local garden supply stores.

Once LDD 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.

Gypsy Moth Burlap Banding

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 2-3 days to destroy them

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 a bait inside their lid that smells like female LDD moth pheromone for attracting males.
  4. Once captured, put the moths in a container of soapy water and leave them for 2-3 days, then dispose of the contents.

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

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
  3. are scraped. Try not to leave any residual eggs in bark ridges or crevices.
  4. Empty the contents of your catchment container or bag into a bucket of soapy water
  5. Leave the eggs sitting in the bucket for 2-3 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

LDD moth caterpillars 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. LDD moth caterpillars don't appear to like ashes, sycamores, butternuts, black walnuts and dogwoods.

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.

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 LDD moth is a parasite of the egg. It is now commonly found wherever LDD moths are and has become an important natural control.

Also, LDD moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. The virus and bacteria escalate when populations peak. TheLDD 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 moth populations peak.

Property owners are responsible for managing trees (and pests) on their property. You are encouraged to monitor trees on your property - look for egg masses in winter, caterpillars in spring, and moths in July and August - and take action to remove LDD moths as often as possible.

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.

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.

The hairs of the LDD moth 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. If you are experiencing any sort of reaction, please contact your family care physician for medical advice.