Protect your Trees: Lymantria Dispar Dispar (LDD)

The LDD lifecycle has four stages:

1. Egg Mass Stage (Late August to early May)
2. Caterpillar Stage (Early May to mid-July)
3. Pupa Stage (Mid-July to early August)
4. Moth Stage (Late July to mid and late August)

The timing of each stage depends on climate and location.

Egg Masses:

• Covered in tan-coloured hairs
• Most often found on tree trunks, branches and on old leaves

Cocoons/Pupae:

• Dark brown, shiny shell
• Hairs sticking out of the shell
• Often found hanging on tree trunks, underside of branches and leaves

Find step-by-step instructions for removing LDD under managing LDD.

• Can grow up to 6 centimetres in length
• Dark and hairy
• Small and black (early stage of growth)
• Five pairs of blue dots and six pairs of red dots on the back (fully grown)

Find step-by-step instructions for removing LDD under managing LDD.

LDD FAQs / Burlap Installation Fact Sheet

Below are various LDD management options that residents may use to lesson the impact of LDD.

April to May

Both the cocoons and the egg masses tend to be located on the underside of branches and on the trunk of the tree. You may also find both attached to clumps of leaves, lawn furniture, wood piles and structures. It is important to remove them during this stage because it will greatly, reduce the number of caterpillars feeding on the trees.

To remove the egg masses, follow these steps:

1. Identify egg masses and pupae on your tree(s).
2. Wear gloves and long sleeve shirts to prevent any skin irritation.
3. Hold a small container below the location and scrape the egg masses and cocoons off your tree(s) into it. Ensure that as many eggs as possible are removed. A vacuum can also be used to remove eggs but must be cleaned out thoroughly once complete as eggs left in the vacuum will hatch.
4. Dispose of the eggs into a bucket of soap and water, stir them in and leave for two days (48 hours). Then dispose of the contents in your compost or green bin.
5. Ensure you do a thorough job of raking up leaves from last fall, especially around affected trees as the egg masses attached to leaves last fall will now be on the ground. Eggs can survive on the ground and will hatch in the spring.
6. Check other yard locations, such as gardens, firewood piles, lawn furniture etc., as egg masses and pupae could exist there too.

April to June

• If trees are severely infested, many egg masses are visible, insecticide may be a viable option.
• Homeowners should contact a licensed tree care company to discuss the best options.
• Some products have very tight timing windows for application to be successful and often require more than one treatment; if an opportunity to treat trees is missed this year, homeowners may want to reserve a spot for next year.

May to August

In the spring and into the summer, caterpillars can be handpicked. Caterpillars can be removed and disposed of by submerging them in a bucket of soapy water for a day or two.

To trap caterpillars, follow the steps below:

1. Wrap burlap* around the tree’s trunk at chest height. Make sure the ends overlap.
   * If you do not have access to burlap, other fabric can work as well. Please avoid using tape or grease products as they are more likely to catch/harm other animals and insects and may also cause damage to the tree. As caterpillars get larger, they will also be able to move over these items.
2. Tightly tie a piece of string around the middle of the burlap/fabric piece. String may also be tied around the base of the burlap.
3. Fold the top half of the burlap over the bottom half to form a skirt/ tent-like structure. Caterpillars will seek refuge under the burlap layers during the day and will become trapped in the fold preventing them from returning to the top of the tree to feed on leaves.
4. Check burlap bands daily, remove the caterpillars and submerge them in soapy water for one to two days. Be sure to check under both layers of burlap. Checking daily will also help to ensure no other animals have become trapped in the band.
5. After a minimum of one day, dead caterpillars and soapy water can be disposed of in compost piles or placed in the green bin.

Note: check your burlap bands daily to ensure birds or any other wildlife don’t get unintentionally caught. If you come across injured wildlife, contact your local Animal Control Services or Wildlife Rescue:

• Toronto Wildlife Center's website
• Shade's of Hope website
• Procyon Wildlife website

They are most destructive in their caterpillar stage as they eat leaves from a large variety of trees. Most healthy deciduous trees can grow a second set of leaves, but conifers are more vulnerable because they aren’t able to produce new needles. Repeated defoliation can cause considerable stress to the tree which can weaken its defenses to other pathogens and vectors. Factors such as drought, during defoliation, can also increase the amount of stress on the tree. Frequent irrigation will help to lesson the stress and promote the second flush of leaves.

Burlap can be purchased at most local hardware stores:

• Home Depot
• Home Hardware
• Walmart
• Canadian Tire

LDD caterpillars do not bite or sting, but many people have an allergic reaction from coming into contact with LDD. This bite like rash is likely caused by the little hairs on the LDD caterpillar coming into contact with bare skin. You may not come into direct contact with the caterpillars but their little hairs can fly through the air and land on skin or clothes, etc. Histamine found in the caterpillar's hair can cause red, itchy bumps to form. The rash is not contagious. Depending on how sensitive you skin is may effect how long it takes to stop itching.

Wearing long sleeves, pants tucked into socks, gloves and hats may help prevent your skin from coming into contact with the hairs. Especially when handling caterpillars or egg masses when clearing off your tree(s). Consider washing clothing worn outside each day to remove hairs that might still be attached.

LDD outbreaks can last two to three years. Based on estimated populations from 2020 and 2021 (egg mass surveys), these numbers will likely repeat again this year (2022). A defoliation survey (July 2021) and an egg masses survey (Fall 2021) was conducted to help make 2022 predictions about the LDD population. Town staff will continue to monitor municipal trees throughout 2022 to determine 2023 populations.

Town staff are back out this spring removing egg masses from, Town owned, boulevard trees. Only egg masses within reach from the ground, using a backpack vacuum with wand extension, will be removed from boulevard trees. Priority will be given to trees in hot spot areas first. Other streets will be worked through systematically as staffing time allows.

Unfortunately, the Town does not have the capacity to take requests to remove egg masses in specific areas in EG. Through ongoing monitoring Parks staff are aware of the streets with concerning amounts of egg masses and will be working systematically through each street. We are not currently asking residents to contact the Town with egg removal requests.

NPV, nuclear polyhedrosis virus, a virus that is host specific and does not affect trees, pets, or people.

Entomophaga Maimaiga, a naturally occurring fungus helps to reduce the population of LDD when it increases to high levels. It is not dangerous to humans or pets.

Multiple species of birds, squirrels, chipmunks, raccoons, skunks, and native insects are also natural predators of LDD.

Unfortunately, conifers are not able to regenerate needles, if severely defoliated they are not likely to recover or survive. Contact an arborist for private tree assessments and removal services.

Residents that are considering tree removals do not require a tree removal permit from the Town of East Gwillimbury.

Yes, residents have the option to treat their private trees.

Bacillus Thuringiensis var. Kurstaki (BTK) spraying is one option. BTK is a naturally occurring bacterium used to kill and control caterpillars. The caterpillars will stop feeding immediately after ingesting BTK. When used as directed, it has no effect on birds, earthworms, or beneficial insects such as honeybees and ladybugs. The first application should be applied when leaf buds first start to open, and the second application should occur approximately one week later. BTK becomes inactive after about a week and is harmless in the environment.