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Gypsy Moth in Hamilton

Gypsy Moth in Hamilton


Gypsy Moth Egg Mass. Size compared to household keys.

Surveys completed by HCA and the City of Hamilton have identified several areas with high levels of gypsy moth populations. As a result, there will likely be localized tree defoliation. HCA staff will be taking several steps to minimize and monitor the gypsy moth impact and population.

HCA surveys for gypsy moth egg masses in January and February each year. These surveys occur throughout the Dundas and Ancaster Area, mainly through the Dundas Valley Conservation Area (DVCA). The east and west ends of the DVCA are surveyed in addition to Spencer Gorge.

Gypsy moth egg mass surveys are an accepted way of predicting defoliation rates for the upcoming summer months. Two survey methods are used by HCA to count gypsy moth egg masses, Kaldar plots and walking transect method.

  • Kaldar plots are standardized 10x10 metre plots in which all gypsy moth eggs masses are counted along with the number of trees and the species of tree.
  • Walking transects involve walking trails throughout the Conservation Area and recording egg masses observed. This is typically completed in lower infestation areas.

The results of our surveys indicate that noticeable defoliation will likely occur within the Dundas Valley just east of the Hermitage parking lot, south of the Hydro lines. High concentrations of gypsy moths were also found in a relatively small area of the east end of the Dundas Valley Conservation Area, south of Little John Road. These areas of higher infestation seemed to be fairly isolated and impacted mainly preferred gypsy moth trees species such as oak, cherry and beech. High concentrations of gypsy moths were also found in a relatively small area of the east end of the Dundas Valley Conservation Area, south of Little John Road.

In these locations it is likely there will be some tree mortality. This is expected due to the stress defoliation will have on trees that may already be in a weakened state as a result of impacts from the fall canker worm outbreak in the spring of 2016 and the subsequent drought that summer.

The City of Hamilton has also conducted Gypsy moth egg mass surveys in Dundas and Ancaster. Staff are working with the City of Hamilton forestry department to collaborate on surveys and to share results. More about the City of Hamilton and Gypsy Moths.


Gypsy Moth Caterpillar

About the Gypsy Moth

The European Gypsy Moth (Lymantria dispar L.) has been a forest pest in Canada for nearly a century. It was accidentally introduced into the United States in 1869 in a failed attempt to start a silk industry. It was first found in Canada in Quebec in 1924 and then in New Brunswick in 1936. It is now established in Ontario, Quebec, New Brunswick and Nova Scotia and British Columbia.

This species is able to travel by attaching itself to various objects, and is considered the most significant tree defoliator in North America. Caterpillars are able to feed on more than 500 different tree species - deciduous and coniferous - and can be transported by wind. They prefer to feed on the leaves of species such as willows, aspens and particularly oak, but will also feed on beech, black walnut, serviceberry and cherry. As the caterpillar matures it will also begin to attack coniferous trees including pine and spruce. They don’t appear to favour ashes, sycamores, tulips, cedars or sumacs.

Defoliation from the feeding of Gypsy Moth caterpillars results in added stress to a tree, and can eventually result in death after several consecutive years of this stress. A single Gypsy Moth caterpillar can eat an average of one square metre of foliage before it enters the cocoon stage. Each egg mass contains about 300 eggs.


What do Gypsy Moths Look Like?

There are four stages in the gypsy moth’s life cycle, all which appear very different. In order to control these pests, it is important to be able to recognize each life stage.


Stage One: Egg Mass
Adult females lay egg masses in late June through August. Eggs are laid in buff-coloured masses about 3-4 cm long and 1-2 cm wide. A live egg mass has hundreds of tiny, hard and round eggs that can be felt within them. Hatched egg masses are lighter in colour, have tiny exit holes on their surface, and will not feel hard inside. Egg masses appear like the texture and colour of a car chamois. They can be found on tree trunks, crevices in tree bark, rocks, outdoor structures, vehicles, and the sides of buildings. The gypsy moth egg mass contains thousands of tiny eggs which can easily carried by wind currents for distances up to one kilometre.


Stage Two: Larvae
When eggs hatch in the spring, very tiny (and very hungry) larvae, or caterpillars, exit the egg mass and begin to travel to their food source—the leaves of trees. The gypsy moth caterpillar grows to be about 6cm long, consists of 11 segments, and is partly covered with course black hairs. Each segment has a pair of coloured dots: the first five segments have blue dots, and the last six have red spots.


Stage Three: Pupae
Once the invasive feeding stage is over, the mature caterpillar will commonly seek a protected area on a tree or other structure, such as a crevice in tree bark or a crack in a rock, to enter their “cocoon” stage and become a fully fledged moth. The cocoon, or pupae, is about 3cm long and dark brown in colour. It has a hard and somewhat shiny appearance. This stage lasts about 10 days in female and 13 days in male gypsy moths.


Stage Four: Adult
The adult, or moth stage of the life cycle, produces very different looking males and females. The adult female is white with a few dark-coloured stripes across its wings, and has prominent white fuzzy head. Despite having fully-functional wings, the female does not fly, but relies on the release of pheromones (chemical attractants) to lure males to the site where she will lay her eggs. The adult male is a mottled dark beige to brown colour with feathery brown antennae. During this week-long stage, the adult moths do not feed and focus all of their energy on reproducing.


Should I worry about Gypsy Moths on my property?

Yes, and for several reasons:

  • Foliage Loss:
    • The loss of leaves can weaken trees even though the majority of trees will produce new leaves later in the summer season. After repeated defoliation, trees can die (usually a few years of defoliation in a row).
  • Caterpillar Frass (Poop)
    • Consuming so much leaf matter in such a short period of time, the amount of fecal matter, or “frass”, produced by caterpillars can become overwhelming. Frass can quickly cover driveways, patios, picnic tables, and other areas frequently used in your yard, and can become a nuisance to clean up and to endure during outdoor activities.

What can I do to control Gypsy Moth on my property?

Private landowners can do a number of things to keep gypsy moths under control on their property:

Egg mass scraping
Removing egg masses in the fall or winter is the most effective way of removing a large numbers of potential gypsy moths as each egg mass can contain over 300 eggs.

  • How to: Scrape egg masses off into a container of soapy water and leave for 1-2 days. Alternatively, scrape them into a bucket and crush or burn the eggs.

Caterpillar removal
As the caterpillars mature (late June to early July) change sticky bands over to burlap bands, called hiding bands. Tie burlap or cloth bands around the tree trunk allowing a hiding space (a flap) under the fabric for caterpillars to seek refuge in the heat of the day. This is then removed daily and the caterpillars killed


Biological pesticides
Commercial tree companies can be contracted to spray Btk products. Btk consists of a dormant bacterium that contains a potent toxin lethal to gypsy moth caterpillars. When applied to infested areas, this toxin becomes activated in the gut of a caterpillar, disrupting its ability to eat, and weakening the individual to its death. This is sprayed on the foliage of the tree. Btk also kills any of our native moth and butterfly species that also eat the leaves within 10 days of spray.


Female Gypsy Moth

Natural Predators of Gypsy Moths

Predators of the Gypsy Moth include:

  • Other insects: wasps, flies and beetles
  • Birds: chickadees, blue jays, robins and nuthatches
  • Animals: chipmunks, squirrels and raccoons
  • Diseases, caused by bacteria, fungi or viruses contribute the most to keeping population levels within a normal range. These most common and effective of these include:
    • Entomophaga maimaiga, a fungus native to Japan was deliberately released in the United States around 1910-1911 to help control gypsy moths. Although the exact means by which this fungus made it to Canada are not known, its presence in our forests has become quite evident as it has been responsible for bringing past gypsy moth infestations under control. The amount of wet weather experienced in the spring months is directly related to the success of this fungus, with wetter springs showing greater declines in gypsy moth caterpillars than in drier springs. Caterpillars killed by this fungus appear shriveled and elongated, hanging in a vertical position
    • Nuclear Polyhedrosis Virus (NPV), was also released in the United States in the 1960’s. While most caterpillar mortality can be attributed to the Entomophaga maimaiga fungus, it has been shown that NPV controls caterpillars effectively, and has been responsible for mass die-offs. NPV is directly specific to gypsy moth caterpillars, and does not affect any other species. Caterpillars killed by this fungus hang downwards in a “V” shape and emit a dark fluid.

What is the HCA doing on its lands in regards to gypsy moths?

HCA staff will be taking several steps to minimize and monitor the gypsy moth impact and population:

  • Banding trees with sticky tape to try and catch the hatching gypsy moths before they start to defoliate the trees. HCA staff will be out banding trees through the first weeks of May 2017. Bands will be changed as necessary.
  • Defoliation surveys will be completed by HCA staff in the high egg mass count locations to track to impact of the gypsy moths.
  • Pheromone traps may be deployed in lower infestation areas to try and kill adult male gypsy moths before they mate.

Homeowner resources:

These are provided as information only.
City of Hamilton Gypsy Moth Info
Government of Canada Gypsy Moth Info
Ontario's Invading Species Awareness Program Gypsy Moth Info
Virginia Tech/Virginia State University Gypsy Moth Info
University of Maryland Gypsy Moth Info
City of Toronto Gypsy Moth Info
Conservation Halton Gypsy Moth Info

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