Gypsy Moth (lymantria dispar dispar)

Gypsy Moth

The European Gypsy Moth (lymantria dispar dispar) is a non-native invasive species that in its larva stage, the caterpillar eats tree leaves causing tree and forest stress. If the larvae population is high, they can defoliate whole trees and forests in a short amount of time. Lymantria dispar dispar (LDD) prefer oak trees, but will feed on a variety of hardwood tree species. Under normal circumstances, defoliation caused by LDD will not kill a tree. However, trees can decline to the point of death in some cases when defoliation is combined with tree age, drought, disease, or other insects.

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

Action Taken by Township Council

At the August 10, 2020 Council Meeting, Township Council discussed the concerns raised as a result of LDD. Township Council adopted the following resolution:

“WHEREAS there are extensive areas across southwestern Ontario, including Waterloo Region, where there is evidence of a significant impact on the tree canopy attributed to the presence of an infestation of the gypsy moth;

AND WHEREAS the defoliation of the canopy places a significant hardship on trees which over several years can weaken the tree sufficiently that it becomes vulnerable to other diseases or insects leading to further decline or the tree dying;

AND WHEREAS this issue associated with the gypsy moth is present in both public and private landholdings, and, crosses municipal boundary jurisdictions;

AND WHEREAS a patchwork approach to surveillance and mitigation treatment will not lead to a successful outcome to curb the gypsy moth infestation;

NOW THEREFORE THE COUNCIL OF THE CORPORATION OF THE TOWNSHIP OF NORTH DUMFRIES RESOLVES:

THAT the Ministry of Natural Resources and Forestry be requested to undertake a robust surveillance program in the Fall of 2020 to identify the hots spots and to measure the density of the gypsy moth population within southwestern Ontario;

AND THAT the Ministry advise affected Municipalities of the results arising from the surveillance program and to recommend a framework for a coordinated approach to curb the gypsy moth population to be delivered in 2021;

AND THAT the Ministry embark upon a treatment program partnership with willing Municipalities as part of a broader strategy to deal with the gypsy moth infestation;

AND THAT this Resolution be forwarded to the Minister of Natural Resources & Forestry, Mike Harris Jr, Parliamentary Assistant to the Minister of Natural Resources & Forestry, and, to Cambridge MPP Belinda Karahalios;

AND THAT this Resolution be forwarded to the Region of Waterloo, the area municipalities within Waterloo region, the County of Brant, and, the City of Brantford.”

Township Council received correspondence from the Ministry of Natural Resources and Forestry in response to the above resolution that indicates that that the Province does not carry out insect control programs on private land. Landowners wishing to reduce impacts on their property have the option to have trees sprayed with BTK (Bacillus thuringiensis) in the spring by registered pesticide application company.

To support landowners in the management of LDD, the Ministry of Natural Resources and Forestry (MNRF) and its partners have developed fact sheets that provide information and outline best management practices. For more information, go to the Ontario's Invading Species Awareness Program and the Invasive Species Centre. MNRF also conducts aerial surveys to delineate the area and severity of any outbreak. Surveys of this year’s infested areas are now complete, and data is expected to be made available in the fall of 2020.

Management by Property Owners

Property owners are encouraged to monitor the trees and pests on their property. Hardwood trees like oaks, maples, beech and walnut need to be monitored for the presence of LDD.

Environmental Stewardship Consultation

The Township has arranged for the services of Albert Hovingh, a Registered Professional Forester, to provide environmental stewardship consultation about the LDD and how property owners can deal with this element in their trees. This consultation service is offered at no expense. If you wish to seek the professional services of Albert Hovingh, please contact him directly as follows:

Albert Hovingh, RFP
Region of Waterloo Principal Planner, Stewardship Planning
Telephone: 519-575-4813
Email: ahovingh@regionofwaterloo.ca

Life Cycle

To manage the spread of the LDD, it is important to know its life cycle. The caterpillars are dark colored and hairy, characterized by five blue dot pairs and six red 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 LDD life cycle are larva/caterpillar, pupa, adult moths, and egg masses. The earlier and more often the pest’s life cycle can be interrupted, the more successful we will be in managing the pest.

Gypsy Moth Life Cycle

Hand Picking: May to July

Handpicking caterpillars is most effective on small newly planted trees, shrubs, and plants infested. 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 for a few days, then dispose of the contents.

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.

Burlap Banding: June to August

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.

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 stem/trunk of your tree
Tie twine or rope around the center or slightly below the center 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.

Burlap Wrapping: July to August

Wrap burlap lower on the trunk of the tree to trap the female moth (that cannot fly) before it crawls up the tree and lays eggs. This is the same method used for the larger caterpillar stage. Once captured, leave the moths in soapy water for a day or two, then dispose of the contents.

Pheromone Traps: July to August

Hang pheromone traps in trees to attract male moths, which prevents them from mating with female moths and producing eggs. Once captured, leave the moths in soapy water for a day or two, then dispose of the contents.

Destroy Egg Masses: November to April

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

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

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 a day or two, then dispose of the contents

GRCA Land Management

The Grand River Conservation Authority looks after the Grand River watershed which includes forest management. Please see the December 2021 update on the LDD 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 1980s 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 LDD.

In Ontario, LDD populations 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, LDD 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 occur every 7 to 10 years. See the Province of Ontario website for more information.

There are four (4) stages of LDD:

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. 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.

Frequently Asked Questions

How much damage can the LDD 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 caterpillar?

The LDD caterpillar 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. LDD do not appear to like ashes, sycamores, butternuts, black walnuts, or dogwoods.

Are there any control factors?

Natural control factors 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 LDD is susceptible to several naturally occurring diseases caused by bacteria, fungi, and viruses. The virus and bacteria escalate when LDD populations peak. The LDD 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.