Gypsy Moth Aerial Spray Program 2019

Gypsy Moth Aerial Spray Program 2019

Gypsy Moth Egg Mass. Size compared to household keys.

Gypsy moth is a non-native invasive species that defoliates trees. The Gypsy moth prefers oak, sugar maple, beech and white pine trees, but may affect other species as well. The life cycle of the Gypsy moth is very similar to many other native moth species, consisting of five distinctive life stages: egg, larva (caterpillar), pupa and adult. A summary description of each stage in their life cycle can be found below.

The Hamilton Conservation Authority (HCA) has surveyed yearly for Gypsy moth egg masses since 2004. Surveys have been conducted throughout the Dundas and Ancaster area, mainly in the Dundas Valley Conservation Area (DVCA). Surveys are completed in January and February each year. The data collected from the surveys conducted this year indicated that severe defoliation is expected in the summer in specific areas. In order to reduce the potential for tree mortality and impacts on forest health, HCA will be conducting a Gypsy moth aerial spray program to help reduce Gypsy moth infestation levels.

Where will the Aerial Spray Program take place?

In 2019, Hamilton Conservation Authority will aerial spray a total of 3 hectares within the Dundas Valley Conservation Area. One specific area is targeted to be sprayed, an area east of Sulphur Springs Road along the main loop trail in the Dundas Valley Conservation Area. This area is identified on the map below. Trail closures in this area will be required during the aerial spray program.

 How and when will the spray program be completed?

Aerial spraying will be conducted by a single engine helicopter with an ultra low volume spray system. During spraying, the helicopter will fly approximately 10-30 meters (50-100 feet) above the treetops between 5am and 8:30 am. The second and final spray will take place on Saturday, June 8, 2019.  Monitoring will occur post spray to see how effective it was and how the trees respond via leaf out.

What will be sprayed?

A bio-pesticide will be used to control Gypsy moths. The bio-pesticide is registered as Foray 48B Biological Insecticide Aqueous Suspension, containing active ingredient Bacillus thuringiensis, subsp. Kurstaki strain ABTS-351, (PCP# 24977) under the Pest control products Act (Canada).

How can I receive updates about the aerial spray?

Updates on the aerial spray program will be available on HCA’s Facebook page and Twitter feed @Hamilton_CA. For more information or if you would like to be notified when the spray dates are determined, please call 905-525-2181 ext. 100.

Please note that the City of Hamilton will also be conducting an aerial spray program for gypsy moth and information on their program can be found at

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.

What are the impacts of Gypsy Moths on my property?

  • 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?

Hamilton Conservation Authority recommends that landowners participate in the control program for Gypsy Moth by scraping and destroying egg masses, catching and destroying caterpillars. Your choice of control method is closely linked to the Gypsy Moth’s stage of development, and is described below by season. 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

Late April-early May - Place sticky barriers, or bands on the tree trunk.
Wrap duct tape around the tree trunk and apply a thin coat of sticky material (ready-to-use products are commercially available in most garden centres) to the duct tape. This prevents young caterpillars from crawling up the tree. This control method will effectively trap only young caterpillars that are already crawling on trees or that emerge from egg masses that are situated low on a tree trunk or on other buildings and objects.

sticky bands to catch caterpillars

Late May-August - Replace sticky bands with burlap (cloth) bands.
Trap and destroy caterpillars by placing burlap (cloth) bands on trees. Wrap burlap that is approximately one metre wide around the tree trunk, tie it at the middle with a rope and fold it. Caterpillars feed at night and hide during the day in shelters that protect them from the heat. They will congregate under the burlap. Destroy caterpillars that emerge from under the burlap late in the afternoon before they crawl back to the canopy to feed.

burlap removing caterpillars

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

Over time, gypsy moth numbers will decline naturally due to the impacts of natural predators and introduced viruses. This can take five years or more to occur.

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 in a V shape.