TBA Sponge Moth/LDD (formerly known as Gypsy Moth) Moth Management Program FAQs

What are LDD Moths? 

Sponge Moth/LDD (formerly known as Gypsy Moths) are an invasive insect from Europe and Asia. LDD Moth caterpillars feed primarily on the leaves of deciduous trees. Caterpillars chew small holes in leaves and can potentially decrease canopy leaf coverage. They are five to 60 millimeters long, dark and hairy with five pairs of blue dots and six pairs of red dots on the back. 

How much damage can they cause? 

High levels of LDD Moth caterpillars can cause trees to experience a loss of leaves, which could lead to weakness and make them more susceptible to diseases or weather fluctuations. As observed at Thunder Beach in 2020, they can strip a mature oak tree of all its leaves in less than a week! Efforts to decrease LDD Moth populations will help mitigate impacts to the tree canopy in the community. Most trees are able to withstand some defoliation. Concern exists when trees suffer multiple years of severe defoliation. Many trees do not recover after the 3rd year of defoliation and 2021 will be the 3rd year of a major infestation in the Thunder Beach community. 

What types of trees do LDD Moth caterpillars affect? 

They are known to feed on hardwood trees such as oak, maple, ash, birch, cherry, elm, hickory, willow and apple species. Other deciduous trees and even conifers such as pine or spruce could be susceptible when LDD Moth populations are high. 

Why does it matter if trees lose a few leaves from hungry caterpillars? 

As the caterpillars grow, they consume more leaves. As the growth cycle winds down in late June, trees can look as if they have lost their leaves overnight. Healthy trees are usually able to grow back their leaves within the season during the first two years of an infestation. However, several years of defoliation weakens trees and can have negative impacts on long-term health. 

The tree canopy provides health, social, environmental, and ecological benefits to communities. 

Trees help to: 

  •  Improve air quality 
  •  Provide shade. Reduce energy demand for cooling in summer and heat in winter 
  •  Prevent flooding 
  •  Increase property values and aesthetics and strengthens communities
  •  Improve emotional well-being and mental health (stress reduction) 
  •  Increase outdoor activity and walkability, leading to improved health
  •  Provide habitat for birds and other wildlife 

Why are LDD Moths such a nuisance? 

Besides defoliating trees, LDD Moth caterpillars can become a nuisance crawling everywhere including up the sides of homes, rocks, on outdoor toys, decks and patio furniture. You can hear them munching on leaves and their droppings (“Frass”) smell and cause a mess. 

Can LDD Moths affect my health directly? 

It is recommended that residents avoid exposure to LDD Moth caterpillars. Children should be discouraged from playing with any LDD Moth caterpillars. Exposure to LDD Moth caterpillar hairs, silken threads and shed skins can cause welts and patchy skin rashes that can persist for 4-5 days and upper respiratory tract irritation in some people. (this happened to a few of us at Thunder Beach last season) 

Aerial Spraying Product Information: 

Product information: Bacillus thuringiensis subspecies kurstaki (Btk), is a naturally occurring bacteria found in soil and a substance used frequently in organic agriculture to manage LDD Moth populations. 

Is Btk safe for humans? 

Btk is an effective pesticide that has been shown to successfully manage LDD Moth populations. It has been extensively studied by Health Canada and the US Environmental Protection Agency (EPA). Research shows that Btk poses minimal risk to human health when used as directed. Btk is approved by Health Canada for aerial use over urban areas. Btk is not expected to have adverse effects on vulnerable populations including children with asthma, people with weakened immune systems, pregnant women or the elderly. Individuals who have concerns should take reasonable precautions to avoid exposure during an application period. 

For more information on Btk, consult the fact sheet provided by Health Canada. 

Is Btk safe for animals? 

According to Health Canada, Btk is only toxic in the caterpillar stage of the LDD Moth life cycle. Btk does not affect adult moths and butterflies, including the Monarch Butterfly, as it is not in the caterpillar stage at this time of year. Btk does not affect other insects, honeybees, fish, birds or mammals. Btk is not considered a risk to pets or animals. That said, it is recommended to bring pets indoors before spraying begins. This will reduce pets bringing Btk indoors. 

How does Btk affect the environment? 

Once applied, Btk biodegrades quickly in approximately 1-4 days through exposure to sunlight and microorganisms. There are no groundwater contamination concerns, as Btk does not travel through the soil beyond 25 cm. 

When will spraying work occur? 

There is a very narrow window in which the application of aerial spray will be effective against LDD Moths. (mid-May to mid-June) Treatment is restricted to the late spring when LDD Moth caterpillars are present and active. (small, hungry and feeding) Zimmer Air Services plan to spray between mid-May to mid-June 2021 and will provide updates on their website. The work is time sensitive and based on when caterpillars hatch, foliage and weather conditions.  

Why plan an aerial spray control program in the Thunder Beach community in 2021? 

Aerial sprays are conducted in response to large, widespread increases in LDD Moth populations, and the high risk of loss to the tree canopy. 2021 will be the 3rd year of a LDD Moth infestation bringing an increased risk of permanent damage to the trees in our community. In the early ‘90’s, aerial spraying was successful at lowering LDD Moth populations at Thunder Beach and the tree canopy was protected. Left untreated, LDD Moth caterpillars will cause defoliation and decrease the health of Thunder Beach’s trees. The program is intended to help manage the LDD Moth population. 

Spraying this spring (2021) is the best approach for the health of trees, our environment and residents. 

Helpful suggestions re: Btk spraying:

While no special precautions need to be taken, the following measures may be considered by residents living in treatment areas:

  • Whenever possible, remain indoors for 30 minutes after spraying to allow for the droplets to deposit
  • Bring laundry, toys, cushions and pets indoors before spraying begins.
  • Practice good personal and food hygiene (e.g., 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, BBQs, play equipment and sandboxes and/or rinsing them off with water after spraying is finished
  • Minimize opening and closing windows and doors during the spraying
  • Shutting off the heating/cooling vents or selecting the recirculate setting. 

It is recommended that you cover all surfaces you would prefer not to be exposed to a film of spray or wash with water soon after spraying.  

The spray does not damage automobile, trailer or boat paint or finishes.  It can be washed off with water soon after the spray.  If left to harden it may take more effort to wash off.  

Is it good enough to just remove the egg masses or put burlap or traps on trees? 

Thank you for your efforts trying to reduce LDD Moth populations on your property. These Integrated Pest Management techniques work with limited success. Egg masses are still located in the upper section of trees that can’t be reached and they can also be found under rocks or attached to wood piles. Each egg mass can have up to 1,000 eggs so it doesn’t take long for caterpillars to travel and appear on the trees. LDD Aerial spray helps manage the population and has a greater impact protecting the trees in the entire community. 

What else can I do to help protect trees on my private property? (in addition to signing up for aerial spraying when planned in our community.)

  • MID-MAY to MID-JUNE: Aerial Spray Program (recommended professional program, time sensitive application to be effective at controlling LDD moth.) 
  • MAY-JULY: Burlapping. Install a burlap skirt around the trunk of the tree. LDD Moth caterpillars will crawl under the burlap to find shade during the day, and can also pupate in the burlap. Check all layers of the burlap once daily and collect, crush or otherwise destroy pupae/cocoon when you see them and place LDD Moths in a bucket of soapy water for a minimum of 48 hours. 
  • MAY-AUGUST – Collect, crush or otherwise destroy caterpillars/pupae/cocoons when you see them. (soak in soapy water for a minimum of 48 hours) 
  • JULY-AUGUST: Install pheromone traps. Male LDD Moths attracted to the pheromone will become trapped. Replace soapy water as the traps become full. 
  • SEPTEMBER–APRIL: Scrape egg masses from all surfaces (e.g. trees, rocks, sheds, eaves troughs) and soak them in soapy water for a minimum of 48 hours to destroy them. Remove burlap and traps. 



The Thunder Beach Association is providing this for information purposes based on our understanding of the problem and proposed solution. The decision to conduct spraying is up to each property owner.