Spongy Moth FAQ’s

About Spongy Moth

What kinds of trees are most affected by the Spongy Moth caterpillar?
Spongy Moths 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. Spongy Moths don't appear to like ashes, sycamores, butternuts, black walnuts and dogwoods.
How much damage can Spongy Moth 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. Most of the hardwood trees can produce a new set of leaves if they have been completely defoliated. But this puts stress on the tree as it uses valuable resources. It is especially stressful if they are trying to do so in a period of hot, dry weather. Fortunately, hardwoods rarely die after defoliation. The best thing you can do is to try to keep your trees as healthy as possible to begin with. If you can, water your trees in those hot, dry periods.
Does the Spongy Moth have any natural enemies?

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 Spongy Moth is a parasite of the egg. It is now commonly found wherever Spongy Moths are and has become an important natural control.

Also, the Spongy Moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. The virus and bacteria escalate when populations peak. The Spongy 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 Spongy Moth populations peak.

For more information, please see the article Natural Enemies of Gypsy Moth: The Goodguys!

What can residents do?
Property owners are responsible for managing trees (and pests) on their property. You are encouraged to monitor trees on your property - look for and remove egg masses in fall and winter, caterpillars in spring, and moths in July and August - and take action. Control measures are often not complicated and easily be undertaken by homeowners. For instructions see the Spongy Moth Lifecycle and Control Measures above.
Do Spongy Moths cause rashes?
Direct skin contact with Spongy Moth caterpillar hairs can result in a rash and/or skin irritation. The hairs of the 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. As a precaution, cover up, wear gloves and long sleeves and avoid touching the caterpillars altogether. If you do experience any sort of reaction, please contact your family care physician for medical advice.

About Aerial Spray Management Program

What is Bacillus thuringiensis?

Bacillus thuringiensis is a rod-shaped bacterium that occurs naturally on dead or decaying matter in soil. It was first isolated in 1902 from diseased silkworm larva. Various strains of Bacillus thuringiensis have been used commercially in the United States since 1958 on insect pests of food, forage crops, and forests. Commercial landscapers and home gardeners frequently use Bacillus thuringiensis for pest control because it is effective, selective, and safe.

There are many different strains of Bacillus thuringiensis that attack specific kinds of insects. For example, Bacillus thuringiensis var. israeliensis is used to control mosquitoes, and Bacillus thuringiensis var. tenebrionis is used to treat some pest beetles specie. Bacillus thuringiensis var. kurstaki (Btk for short) is used to control caterpillar pests such as Spongy Moths.

How does Btk kill caterpillars?
When Btk is ingested by a susceptible caterpillar, the highly alkaline environment of the caterpillar’s gut triggers the Btk bacterium to release a crystalline protein called an “endotoxin” that poisons the insect’s digestive system. The endotoxin acts by killing cells and dissolving holes in the lining of the insect’s gut. When a mixture of food, Btk spores, and digestive juices leaks through these holes into the insect’s blood, it causes a general infection that kills the caterpillar.
How is Btk used?
Btk in its various formulations can be applied using both ground and aerial spray methods. Aerial spraying may be used in forestry and urban areas to ensure adequate coverage and effectiveness. Btk has been used on millions of acres of wooded areas and agricultural crops in many countries worldwide. Btk products are used in Canada to control Spongy Moth, spruce budworm and other specific pests in forestry and urban settings, as well as certain insects that feed on vegetable and fruit crops.
Is Btk a good choice for controlling Spongy Moths on trees?

There are many advantages to using Btk to control caterpillar pests:

  • Caterpillars that become ill or die after ingesting Btk are not considered dangerous to birds or other animals that feed on them.
  • In general, sunlight and other microbes destroy Btk applied to foliage within three to five days, so Btk does not multiply or accumulate in the environment.
  • Perhaps most importantly, Btk does not appear to pose any significant threat to human health or to pets. Btk is often sprayed over large areas from planes or helicopters in formal Spongy Moth control programs over large areas but commercial applicators or homeowners can apply Btk effectively to individual trees from the ground.
How effective is Btk in controlling Spongy Moth caterpillars?

Spraying Btk is not a "silver bullet" solution to the Spongy Moth outbreak. It will not eradicate Spongy Moth but it will reduce populations to more manageable levels to protect tree canopies. Also, it takes time to have effect and will not destroy caterpillars immediately. It can take 2-4 days depending on caterpillar size. Larger caterpillars may even survive the spray event. Aerial spraying Btk is only one “tool” and other management techniques such as burlap banding should also be used.

Ultimately it will be natural causes such as natural enemies (virus, fungus, parasitic wasp, etc.) that will cause the outbreak to eventually collapse.

If Btk already exists in soil, why do we need to spray trees to control Spongy Moths?
Btk normally is found in the soil but not on tree leaves. As such, caterpillars don’t encounter Btk that occurs naturally in the environment and so do not become infected that way.
Why is spraying from the air seen as more effective than spraying from the ground?

Evaluation of previous programs over the past few decades have shown that aerial sprays are highly effective for controlling many forest pests including Spongy Moths. Large areas can be treated in just a few hours. Most droplets reach the ground within 10 minutes of application.

Aerial spraying can treat remote or difficult-to-access areas, providing even coverage throughout the target area. Also, the droplets can penetrate the crowns of even the tallest trees.

What is the formulation of the Btk product?
The registered name of the pesticide that will be used by the City is Foray® 48B Biological Insecticide Aqueous Suspension. It is registered under the Pest Control Products Act (PCP # 24977). It is comprised of 3% Btk bacteria, 75% water and 22% food grade inerts. The term ‘food grade inerts’ refers to a special blend of additives that give the formulation protection against ultraviolet light and help make it stick to foliage. They do not pose any health risks. Btk remains effective for approximately one to four days before it breaks down in the presence of sunlight.
What is the concentration of Btk?
A small amount of liquid covers a large area: 4 litres will cover 1 hectare (2.5 acres). Comprehensive spray drift modelling has been done to ensure accurate and effective application.
Who regulates Btk use in Canada?

Health Canada's Pest Management Regulatory Agency is responsible for ensuring the human health and environmental safety of all pest control products prior to their approval for use in Canada.

Manufacturers must provide the Agency with full analyses of the product formulation, as well as extensive health and environmental data, so that a risk assessment can be carried out by PMRA scientists. Only products that are scientifically reviewed and found to be effective and safe for use with minimal risk to human health and the environment are registered by the PMRA. Btk has been approved by the PMRA for aerial use over urban areas.

Is Bacillus thuringiensis kurstaki (Btk) safe to people?

According to Health Canada, Btk poses little threat to human health either through handling products directly or through indirect exposure such as aerial spraying. The public are unlikely to experience any symptoms if inadvertently exposed to Btk spray, and no special precautions are necessary or required.

Btk is approved by the Pest Management Regulatory Agency (PMRA) of Health Canada and has been in use for over 30 years in urban areas. Btk has been used safely and effectively managing LDD in other aerial spray municipal programs such as Toronto, Oakville, Sarina, and Hamilton.

In addition to the Btk active ingredient, other ingredients called formulants have also been studied broadly and do not have any significant health risks. Formulants normally include water and other ingredients to make the product stick to leaves and needles of trees.

Another subspecies of Bacillus thuringeiensis bacterium, called Bti, has been used to control mosquitos in surface water in the GTA for over a decade as part of the efforts to protect against West Nile Virus. Btk has been used successfully in aerial sprays as well as ground-based spraying for the past 10 years by the City of Toronto to control Spongy Moth populations.

Would humans or other animals be harmed if they accidentally ingested Btk?
Humans and other mammals have highly acidic environments in their stomachs that destroy Btk before it can causes infection. Because the Btk endotoxin requires extremely alkaline conditions to become active (such as those found in the guts of Spongy Moths and other caterpillars). Btk does not affect animals with acidic stomach environments such as birds, fish, and mammals. There is no impact on pets if they are exposed to or ingest Btk.
Is it possible to be infected with Btk?
After a person or animal has been exposed to bacteria of almost any kind, the amount of bacteria in the tissue can be measured. When the amount of bacteria increases over time and damages or destroys tissue, it is said to have caused an infection. If the bacteria is found in the person’s tissue for a period of weeks yet no tissue damage results, the bacteria is said to merely be persistent. Almost all reports of Btk in tissues have been associated with persistence rather than infection. The world is full of microbes that our bodies encounter on a regular basis, but only a tiny few of them cause any problems. Btk behaves like most persistent bacteria and fades away after a short period of time.
Isn’t it better to completely avoid exposure to Btk?
Most North Americans have already been repeatedly exposed to Btk. Because Btk naturally persists in soil and is also sprayed on many crops (including those that are organically grown), it is likely that you are exposed to Btk during the course of your daily life. If you eat fruits and vegetables, you have probably already ingested Btk, probably without any ill effects.
Is Btk really safe to use for treatment of Spongy Moths?

Environmental and health monitoring is carried out by federal and provincial scientists after spraying programs to evaluate any possible effects on humans or the environment. Even with the many years of widespread use of Btk in forestry, agriculture and urban settings, no public health problems have been identified, nor have any significant environmental concerns been raised.

Bt strains have been used by both organic and non-organic farmers throughout the world for many years. Btk is one of the few pesticides acceptable to organic growers, as it is a naturally occurring biological organism, rather than a synthetic chemical. As Btk does not survive in warm-blooded organisms, any Btk residues on food pass through the digestive system without producing any toxic effect. Btk strains are exempt from residue tolerances in the US, and exempt from maximum residue limit requirements in Canada, due to the minimal risk.

Btk’s exceptional safety record extends all the way back to the 1950s, when it first came into use in the United States. After a thorough review of the toxicity of Btk products, including both active and inert ingredients, the U.S. Environmental Protection Agency, Health Canada, the World Health Organization, and many other groups have judged it safe and effective for aerial applications when used according to label directions.

Does Btk spraying pose a risk to residents who might have sensitivities?

Members of the public are unlikely to experience any symptoms and no special precautions are necessary or required. Btk aerial spraying is not expected to have adverse effects on vulnerable populations including children with asthma, people with weakened immune systems, pregnant women or the elderly. However, infrequently there may be some residents who are more sensitive and may experience skin, eye or respiratory irritation.

Although we don't have evidence that Btk will affect any given group of people, individuals with a weakened immune systems or serious food allergies may choose to avoid any potential for exposure by leaving the spray area during the application. People with weakened immune systems may include those with cancer, AIDS, or transplanted organs. If you or someone in your home is concerned and cannot stay indoors or leave the area during the application, you might consider speaking to a health care provider.

What should I do if I experience an adverse reaction?

If you experience an adverse reaction or any worsening medical condition, speak to your physician or, in an emergency, call 9-1-1.

If you would like to report any kind of pesticide incident, please report directly to Health Canada’s Pest Management Regulatory Agency via their Public Engagement Portal Voluntary Incident Reporting Form. The form included in the portal allows you to report on the following: Human Health Incident, Domestic Animal Incident, Environmental Incident.

Will BtK sprays kill other butterflies?

Foray 48B (Btk) is proven to be an effective product in managing Spongy Moth and is also more cost effective, however, it might impact other butterfly or moth caterpillars that may be feeding at the time of the aerial spray. But, most of butterflies, including Monarch butterflies, are not in the caterpillar stage during the aerial spray period and the BtK protein will be degraded shortly. Due to its low residual nature and the narrow spray window of pest development, the non-target impact is expected to be low.

The spray does not contaminate the area with BtK bacteria. Furthermore, only small parts of the forest are targeted for spray. Butterflies outside the spray area are not affected.

Where does Btk go in the environment?

Research shows that Btk used in aerial spray programs has not been shown to have any negative environmental effects. Once applied, Btk biodegrades quickly, approximately 1-4 days, through exposure to sunlight and micro-organisms. There are no groundwater contamination concerns, as Btk does not travel through the soil beyond 25 cm. The United States Environmental Protection Agency categorizes the risks posed by Btk strains to non-target organisms as minimal to non-existent.

When should Btk be applied for control of Spongy Moths?

Timing of Btk applications is critical to successful control of caterpillars. Because Btk is a stomach poison, it must be eaten by the insect in order for it to work and must be applied when there are as many caterpillars as possible feeding in the tree canopies. The factors that affect this are leaf area and caterpillar stage. Leaves should be large enough to provide area for the spray to land on and for the caterpillars to eat. Btk has little effect on the Spongy Moth’s non-feeding life stages (eggs, pupa, and adult stages).

Btk is most effective against young, actively feeding caterpillars. This year there will be two aerial spray applications of Btk set 7-10 days apart. The first event will be timed when 90% of the Spongy Moth eggs have hatched, climbed into the tree canopies, and are actively feeding. This year the first spray event is projected to take place mid-May with the second event 7-10 days later, while caterpillars are still less than 3/8-inch long. This means that some very early and very late emerging caterpillars may not be affected.

Variations in weather and other conditions may alter this timetable. Weather such as wind and rain impacts when Btk can be applied and there may be delays and the spray dates rescheduled.

How will Bacillus thuringiensis kurstaki (Btk) be sprayed?

The product is applied directly to tree foliage by a twin-engine helicopter equipped with an ultra- low- volume spray system. The aircraft flies about 15 to 30 metres above the tree canopies. Residents can expect high audible levels as the helicopter passes over path. The spray application will be conducted by Zimmer Air Services Inc.

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. It only occurs over designated (select) areas.

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

How will I know when the spray is happening?

Aerial spray dates are highly dependent on weather conditions. The actual confirmed spray date will be posted 48 hours in advance on the website and social media.

Residents can request 48 hour advance notice by completing the online registration form on the City’s Spongy Moth webpage or by contacting Forestry Division at 519-759-4150 (x5766).

What happens if the spray is cancelled?
Bad weather or wind may cause the aerial spray to be postponed with little advanced notice. The City will issue a communication to the public 48 hours before each treatment and provide up-to-date information online at Spongy Moth webpage (brantford.ca/spongymoth), through the City’s social media channels (Facebook, Twitter, and Instagram) and through 48 hour advance notification. The spray may be cancelled up to 24 hours in advance if the weather conditions change.
Should I cover items in my backyard?
It is recommended to cover things you don’t want sprayed like patio furniture, outdoor tables, play equipment and sandboxes or you can simply rinse them off with water after spraying is finished. The spray does not damage paints or finishes.
Can my pool remain open?
Btk biodegrades quickly through exposure to sunlight. If possible, cover pools during the spray period. If the pool has not been covered during the spray, test the water to ensure chemistry balance in the water chemistry prior to swimming.
Will BtK sprays take the paint off my car?

No. Some people living in spray areas have reported the presence of a fine dust after the spray, but this easily washes off and does not harm the finish of painted surfaces.

There is a film on my patio furniture; will it come off with water?
The spray does not damage paints or finishes on automobiles, houses, boats or trailers. If it is left to harden, the spray can be removed with water but may require more effort. The sooner it is washed off, the easier it is to remove.


• Bacillus thuringiensis subspecies kurstaki, Health Canada. Retrieved April 28, 2022, from https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports- publications/pesticides-pest-management/fact-sheets-other-resources/bacillus-thuringiensis- subspecies-kurstaki.html

• Commonly asked questions about BTK, Purdue University. Retrieved April 28, 2022, from https://extension.entm.purdue.edu/GM/PDF/GMquestions.pdf

• European Lymantria Moth Spraying, HealthLinkBC. Retrieved April 28, 2022, from https://www.healthlinkbc.ca/healthlinkbc-files/european-lymantria-moth-spraying

• Gypsy Moth Spraying FAQs, Oregon Health Autority. Retrieved April 28, 2022, from https://www.oregon.gov/oha/ph/healthyenvironments/healthyneighborhoods/pesticides/pages/btkfac ts.aspx

• FAQ - Spongy Moth, City of London. Retrieved April 28, 2022, from https://getinvolved.london.ca/gypsy- moth/widgets/87286/faqs#15292

• FAQ – Spongy Moth, Town of Pelham. Retrieved April 28, 2022, from https://www.pelham.ca/en/living- here/LDD_Lymantria_dispar_dispar_Moth.aspx#Spongy-LDD-Moth