Gypsy Moth Spraying

HealthLinkBC File Number: 
Last Updated: 
March 2021

What is the gypsy moth?

The gypsy moth (Lymantria dispar) is an invasive insect and a harmful forest pest. Originally from Europe, the gypsy moth is not native to Canada, but has been found here for over 100 years. They attack over 300 different native and ornamental trees and shrubs.

The life cycle of the gypsy moth has 4 distinct stages: egg, larva or caterpillar, pupa, and adult.

Gypsy moth caterpillar Gypsy moth adult
Caterpillar Adult female (white) and male

Photos provided by the Canadian Forest Service


The adult female gypsy moth lays eggs in masses, in August and September. Eggs are often found on the covered areas and crevices of trees, as well as on items that are under or near trees such as lawn furniture, cars, trucks, trailers, and campers.

Often these egg masses get accidentally transported by people and can be relocated over long distances before starting a new infestation when the eggs hatch in the spring.

Where is the gypsy moth found?

The European gypsy moth has been found in many parts of southern British Columbia, as well as Ontario, Quebec and many parts of Eastern Canada including southern New Brunswick and Nova Scotia.

Why is the gypsy moth a concern?

The gypsy moth caterpillar is a defoliator, which means they eat the leaves of trees and shrubs. This can damage the plant, causing growth loss, stunted growth, or stem deformities, or the plant may die.

In B.C., the gypsy moth is a serious threat to major fruit producers as it eats the leaves of fruit trees such as cherry and apple trees, as well as specific berries such as blueberries. A gypsy moth infestation in B.C. can also impact other industries including agriculture, lumber, and plant nurseries.

Skin rash and possible upper respiratory tract symptoms are linked to human exposure to airborne gypsy moth hairs, silken threads, and skin shed during large-scale infestations. However, large-scale infestations are not expected in B.C., so it is unlikely that exposure to the gypsy moth will affect human health.

How is the gypsy moth population being controlled?

In B.C., the goal of gypsy moth management is “eradication” to prevent populations from becoming established. Canadian and U.S. agencies are working to find and eradicate this invasive pest. As a result, while gypsy moth populations are found in B.C. every year, the insect has not become permanently established in B.C. or in adjacent areas in Western Canada and the Western United States.

Many methods are used to monitor and control the gypsy moth population in B.C. These methods include mass trapping and ground and aerial spraying of the commercial product Foray 48B®, which is used for controlling gypsy moth populations over large or difficult-to-access areas.

What is Foray 48B®?

Foray 48B® is a water-based product containing a bacterium called Bacillus thuringiensis variety kurstaki (Btk). Btk is found naturally in the soil and is known to cause illness in many insect larvae when ingested, including caterpillars of pest species such as the gypsy moth. Larvae are most susceptible to Btk when they are in the early developmental stages.

Foray 48B® also contains a number of inert (inactive) ingredients that improve the performance of the Btk. Many of these ingredients are approved food grade additives and Foray 48B can be used on certified organic farms. No petroleum products are used.

Foray 48B® is not toxic or harmful to people, dogs, cats, fish, birds, reptiles, or insects such as honeybees, beetles, or spiders. Pest control products containing Btk have been registered for use in Canada for about 40 years. It is now the most widely used pest control product in the world.

What happens during aerial spraying?

Aerial spraying of Foray 48B® for gypsy moths is usually done in the spring between April and June and takes place between 5:00 a.m. and 7:30 a.m. Three separate applications are done every 7 to 10 days. These applications are usually required to treat the gypsy moth larvae, which hatch during the treatment period.

Depending on the size of the treatment area, the aircraft used and any weather delays, it may take several mornings to complete 1 application. The treatment area may appear larger than it actually is because the aircraft makes turns in areas outside of the treatment area. Spraying is carefully controlled by GPS navigation equipment and only occurs over designated (select) areas.

You may notice a musty smell and spray droplets on hard surfaces and windows after the treatment. Droplets can be removed with water and a bit of scrubbing, but will eventually disappear on their own.

Residents receive treatment information and schedules through a public notice, at least 24 hours before an aerial application project begins, through the local media, the gypsy moth hotline, websites, and email distribution lists. All schools and hospitals in the affected area are notified in writing at least 24 hours before a spray program starts. Treatment schedules rely on the weather, so for up-to-date information, visit the Ministry of Forests, Lands and Natural Resource Operations and Rural Development (FLNRORD)

Are there any health concerns?

Two extensive public health studies monitoring the impact of spraying on reported illness were conducted in Vancouver and Victoria. Results show no increase in illnesses reported by health care providers (including hospital emergency room visits.) There is no evidence of harmful effects in persons and children with asthma or with weakened immune systems.

If you wish to avoid contact with the spray, it is recommended that you close windows the evening before aerial spraying takes place and stay indoors while your property and nearby areas are being sprayed. You should wait until the spray has dissipated (dispersed) from the air (usually within an hour, sooner in windy conditions) before going outdoors. If you have health conditions and are concerned, you should speak to your health care provider.

In addition to staying indoors during the spraying, you should also follow standard good hygiene practices. These include:

  • Wash your hands after any outdoor activities
  • Wash all fruits and vegetables gathered from the affected areas before eating or cooking

For More Information

Is it an emergency?

If you or someone in your care has chest pains, difficulty breathing, or severe bleeding, it could be a life-threatening emergency. Call 9-1-1 or the local emergency number immediately.
If you are concerned about a possible poisoning or exposure to a toxic substance, call Poison Control now at 1-800-567-8911.

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