The Spongy Moth (Lymantria dispar dispar), formerly known as European Gypsy Moth, is a non-native defoliating insect that feeds on a variety of tree species found in southern Ontario. In Brantford and surrounding areas, the Spongy Moth can be problematic in forested areas with oak dominant communities such as Mohawk Park.
Accidentally introduced in North America from Europe and Asia in the 1860s, the Spongy Moth has thrived with limited predators and can be destructive to local ecosystems. The moth is of concern because during the larva stage of the insect, the caterpillar eats the leaves of trees, defoliating them which in turn may make them more susceptible to disease and damage from other insects.
Although the caterpillars feed on a wide range of hardwood and evergreen trees, they show a preference for certain species such as oak, maple, poplar, and willow trees. Every 8 to 12 years when conditions are suitable, significant increases in populations of Spongy Moths occur. These outbreaks can cause large holes in the leaf surfaces or completely defoliate trees and shrubs in large areas. Continued defoliation of trees can lead to their decline and eventual death.
In Ontario, Spongy Moth outbreaks have peaked in 1985, 1991, 2002, 2008, 2020, and 2021. In the Brantford area, there has been patchy defoliation recorded annually since 2018, with significant expansion of the area defoliated in 2020 and 2021. The Ontario Ministry of Northern Development, Mines, Natural Resources and Forestry (NDMNRF) has indicated this is the worst infestation in Ontario in 30 years.
The City’s integrated pest management
Spongy Moth outbreaks may appear suddenly and may continue for several years in any one location. Natural control factors such as disease, parasites, and predators eventually combine to cause a collapse of these outbreaks. Consecutive years of Spongy Moth infestation can cause severe defoliation which can lead to tree mortality.
Intervention may be required to control continued outbreak levels of Spongy Moth in areas with trees that are at risk of mortality if no action is taken. Eradication of the Spongy Moth is not a realistic management objective since it is well established throughout North America.
Several strategies to address the pest population may be necessary. Strategies that are the least harmful to the environment are initiated first. Control measures include the removal of caterpillars, burlap banding, insecticide application, installation of pheromone traps, removal of egg masses (where possible), and in some cases biological controls. For more information, see the Spongy Moth Lifecycle and Control Measures section below.
In the fall, egg mass surveys can be undertaken to assist with anticipating projected Spongy Moth populations, and whether spraying insecticides, biological control measures should be considered as part of an overall management strategy in subsequent years.
The Forestry Division has contracted a Forestry consultant who specializes in pest management strategies to conduct intensive surveillance in three parks (Glenhyrst Gardens, Mohawk Park, and Mount Hope Cemetery) and the municipally owned trees along two streets (Summerhayes Crescent and Lakeside Drive). In the late October 2021, the consultant conducted egg mass surveys in these areas and concluded that all the surveyed areas are likely to experience significant defoliation in 2022 if left unmanaged.
Aerial spray management program
Based on population surveys conducted in 2021, the City of Brantford is expected to face extreme levels of Spongy Moth this year that could result in a significant loss of trees if no action is taken. Therefore, this spring, the City conducted an aerial spray in select areas with a safe and naturally occurring biological insecticide to limit the effects of the Spongy Moth infestation - the first spray on May 24, and the second spray on June 2.
There are five designated spray blocks and a total block size is 55 hectares. These spray areas will be closed temporarily during the spray and reopen immediately after. Closure signs will be posted.
Details
| Spray Block | Block size | # of properties in 100m buffer |
|---|
| Deer Park (61 Kent Road) |
2 ha |
128 |
| Glenhyrst Gardens (20 Ava Road) |
6 ha |
58 |
| Mohawk Park (51 Lynnwood Drive) |
20 ha |
107 |
| Mount Hope Cemetery (169 Charing Cross Street) |
17 ha |
166 |
| Wyndham Hills |
10 ha |
87 |
| Total |
55 ha |
546 |
Check each spray block map and the list of adjacent properties (within 100 meter buffer) below.
The aerial spray will use Foray 48B Biological Insecticide Aqueous Suspension, containing active ingredient Bacillus thuringiensis, subsp. kurstaki (Btk) strain ABTS-351 (PCP# 24977), under the Pest Control Products Act (Canada). Foray 48B (Btk) is approved by Health Canada for aerial use over urban areas. It has been extensively studied by Health Canada and the US Environmental Protection Agency (EPA). Research shows that Btk used in aerial spray programs has no negative environmental or human health effects.
Btk is a bacterium which occurs naturally in soil and biodegrades quickly in the environment. Btk produces a protein that is toxic only to the caterpillars of specific insect species. When ingested by susceptible insects (early caterpillar stage of Spongy Moth), the toxic protein molecules break down the walls of the insect’s stomach causing the insect to stop feeding. The insect usually dies within two to five days. Btk does not affect adult moths or butterflies or other beneficial insects such as honeybees, pets, birds, fish, or mammals.
For Btk toxins to be activated, the alkaline conditions that exist only in certain insects’ digestive systems must be present. The acidic conditions in the stomachs of humans and animals do not activate Btk toxins, which is why the pesticide is not toxic to humans and animals. There have been no documented cases involving toxicity or endocrine disruption potential to humans or other mammals over the many years of use in Canada and around the world. Studies have shown that even if Btk spores are ingested or inhaled, they are eliminated without any adverse health effects. The fact that Btk is a naturally-occurring, widely-distributed organism in the environment means that the average person would have multiple exposures to this biological agent throughout their lifetime, even if they never came in contact with a formulated product.
Btk has been used in many countries over the last 30 years without health impacts to individuals on medications or vulnerable populations. Most of other municipalities in Ontario – Toronto, Mississauga, Oakville, Hamilton, and London – will be conducting an aerial spray program with this same product this spring as well.
View Spongy Moth Aerial Spray FAQ webpage
No special precautions are required for residents in the spray zone. Individuals who have concerns should take reasonable precautions to avoid exposure during a spray program in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued.
If people wish to avoid exposure, they can consider:
- Remaining indoors during and for 30 minutes after spraying to allow for the droplets to deposit onto the tree leaves.
- Bringing laundry, toys and pets indoors before spraying begins.
- Practicing good personal and food hygiene (hand washing after outdoor activities, especially after gardening; leaving outdoor shoes at the door; washing all fruits and vegetables before eating or cooking).
- Covering lawn furniture, outdoor tables, pools, barbeques, play equipment and sandboxes and/or rinsing them off with water after spraying is finished.
- Minimizing opening and closing windows and doors during the spraying. Shutting off the heating/cooling vents or selecting the recirculate setting.
- Contacting your family physician if you are concerned that a personal medical condition may be aggravated by the spraying.
Foray 48B (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. Infrequently there may be some residents who are more sensitive and may experience skin, eye or respiratory irritation. If you experience an adverse reaction or worsening medical condition, speak to your physician or, in an emergency, call 9-1-1.
Organized and coordinated by the City, the aerial spray follows provincial and federal regulations, guidelines and best practices. During an aerial spray, a two-engine helicopter with an ultra-low volume spray system will fly at low altitudes, about 15 to 30 metres, above the tree canopy. The product is directly applied to tree foliage as the caterpillars must feed on the treated leaves for the insecticide to be effective. Residents can expect high audible levels as the helicopter completes its once-over path.
The best time to apply Foray 48B Btk is in mid-May when caterpillars are small and feeding. Once the leaves are a certain size, the caterpillars have reached almost 90 per cent emergence and the caterpillars begin feeding, the spray window can be narrowed. Once these factors are met, weather conditions are monitored.
Pesticide application is highly weather-dependent. Ideal application conditions consist of: calm winds (1-16 km/h), high humidity (>40%), temperatures between 2 and 25 degrees Celsius, and no precipitation within the spray window dates and ideally not for 24 to 48 hours after application.
Aerial spraying takes place on two days. In 2022, the first spray has been completed on May 24, and the second spray on June 2.
Spongy Moth lifecycle and control measures
The Spongy Moth’s lifecycle is important in managing its impact. There are four main stages of the Spongy Moth lifecycle.
Egg
- This dormant and over-wintering stage lasts eight months from late August to early May.
- Egg masses are fuzzy and tan in color. They range in size from 2-8 cm long and can contain between 100-1000 eggs.
- Eggs are usually laid in dark, sheltered areas such as in bark crevices, on the underside of branches, or in leaf litter, although they can be also be found on a wide variety of surfaces such as rocks, buildings, lawn furniture, and automobiles.
- WHAT TO DO? You can remove egg masses as you see them, before hatching occurs in the spring.
Step-by-step instructions
- Prepare a dull scraper tool (butter knife or plastic paint scraper), catchment container or bag to collect egg masses, and bucket of soapy water (dish soap).
- 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. If the eggs fall on the ground, crush them with the sole of your shoe.
- Empty the contents of your catchment container or bag into a bucket of soapy water.
- Leave the eggs sitting in the bucket for 2 days, then dispose of the contents in the garbage.
- You can also use your vacuum to remove egg masses.
Note: egg masses can be located high up in trees. Care needs to be taken if trying to access anything aloft, especially if using ladders. Some private tree care companies can be hired to provide this service at heights.
Caterpillar
- This is the tree damaging stage and can last about 40 days, from early May to mid-July.
- A single caterpillar can eat an average of one square meter of foliage. They continue to feed, moult, and feed until they are about 6-7cm long. The caterpillars climb up to the tree canopy and also travel to a nearby tree through a method called “ballooning”, where they dangle from long silken threads at the end of branches and are carried away by the breeze.
- The caterpillars of the Spongy Moth are dark and hairy. They have five blue dot pairs and six red dot pairs on their back. They go through 4-5 moulting stages where they shed their skin and each time, they get bigger.
- Once they’ve finished feeding (around mid July), they seek shelter to cocoon.
- WHAT TO DO? Handpicking or Burlap banding can be effective.
- Handpicking caterpillars is still one of the most effective ways to help control Spongy Moths on small newly planted trees, shrubs, and plants. If possible, you can also gently shake the tree, so caterpillars fall from the 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 to destroy them.
- Once Spongy Moth caterpillars grow to about an inch (2.5 cm) in length by mid-June, they do most of their feeding at night and move down the trunk to seek shelter from predators and heat during the day. Reduce the number of caterpillars on the trees in your yard by trapping them.
- Burlap banding is a popular method of control but, if done improperly, can cause more damage to trees than Spongy Moth. For example, foil and plastic wrap should never be wrapped around a tree in place of burlap because they can scar or kill the tree. In addition, sticky tape banding is not recommended, as it can kill all other beneficial insects or birds.
- Step-by-step instructions for burlap banding.
Pupa
- This transformation stage lasts 10-14 days, from mid July to early August.
- After the adult moth emerges, it leaves the empty cocoon behind. The female cocoon is larger than the male cocoon.
- The cocoon can be found on a variety of surfaces including trees, rocks, houses, boats, trailers, fences, picnic tables, etc.
Moth
- This reproductive stage lasts about 10 days, from late July to mid August.
- An adult Spongy Moth’s only function is to reproduce. Unlike other species of butterflies and moths, adult Spongy Moths do not eat anything.
- The female is larger than the male and is cream coloured. The female moths cannot fly. Instead, she uses pheromones to attract male moths.
- Male moths are smaller and brown in colour.
- WHAT TO DO? Pheromone traps can be used.
- The pheromone trap releases a chemical to attract male Spongy Moths where they’re trapped before they can mate with the female moths (and produce the next generation of caterpillars).
- Since each female moth is capable of laying 1000 or more eggs, this has a great impact on the control of the pest.
- The male Spongy Moths can fly strongly and can detect the female pheromone from a considerable distance. Since the pheromone is carried by air currents, it also means that the male moths may fly into the area from any direction.
- For a property of 2,000 - 4,000 sq meters, it is suggested that 5 traps should be used - one trap at each corner of the property, and one trap placed centrally.
- To be effective, the traps must be in position before the adult moths appear. So hang them up in the 1st week of July.
Step-by-step instructions
- You can purchase the traps at various retail stores or online throughout your area.
- Put the traps out when the moths are active after coming out of their pupa stage of growth. Only male moths are attracted to the traps.
- Homemade traps can be created with various designs. The traps should have bait inside their lid that smells like female Spongy Moth pheromone for attracting males.
- The traps should be inspected from time to time and if full, the inserts should be replaced with new ones or additional traps may be added. The lure should last between 3-6 months which is long enough to cover the adult moth period.
- Put the captured moths in a container of soapy water and leave them for 2 to 3 days, then dispose of the contents.
- The traps may be taken down in September for use again the following year with new lures.
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Frequently asked questions
View Spongy Moth FAQ's
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