Lymantria Dispar Dispar (LDD), also known as Gypsy Moths, is an invasive caterpillar that has been found throughout York Region. The outbreak occurs on a cycle every 7 to 10 years. Although they are a nuisance and eat the leaves, the impact will not kill your tree, and the leaves will grow back. The caterpillars do not bite or sting, however, the little hairs on the LDD caterpillar may cause an allergic reaction.

LDD Update:

Residents should begin to remove sticky bands from their trees as the large caterpillars can easily move across them without getting stuck, they are typically most useful for 1st and 2nd instar caterpillars. Burlap bands will still be trapping live caterpillars, though most have started pupating and many have already pupated.  Destroying live caterpillars and pupae within the burlap is also important. We encourage residents to leave burlap up on the trees as there is the potential for female moths to lay their eggs in and on it. This will help to make removal of egg masses easier in the fall. Burlap is still available at the Holland Landing Library and will be available again next spring.

The Town discovered an outbreak of NPV, The nuclear polyhedrosis virus (NPV), part of the family of baculoviruses, is a virus affecting insects, predominantly moths and butterflies. It has been used as a pesticide. Lymantria dispar dispar (commonly known as the gypsy moth) has been successfully contained by releasing gypsy moth baculovirus (NPV) preparations. This is a very positive discovery and we are already witnessing thousands of caterpillars dead at the base of trees which equals lower moth numbers.

Residents are encouraged to continue using burlap to wrap trees for the next few weeks as caterpillars will begin their adult moth transformations. LDD’s have started to pupate, meaning that feeding has slowed and will soon stop completely. Caterpillars will secure themselves to leaves and bark then form a cocoon using their hairs as protection. If removing pupae, please continue to wear long sleeves and gloves as the hairs are present around the casings and can still cause dermatological reactions.

What are Lymantria Dispar Dispar (LDD)?

LDD is a defoliating caterpillar that prefers to feed on oak tree leaves, but will also feed on the leaves of maple, elm, birch, poplar and willow trees. In some rare cases, when their numbers are extremely high, the caterpillar will feed on evergreens such as pine and spruce. The caterpillars tend to only feed and damage trees for a short period of time in June and July. Most trees will put out new leaves when the weather is favourable (with periodic rain).

To learn what types of trees you have on your property, visit the Forests Ontario website.

Life Cycle of LDD 

European Gypsy Moth Lifecycle

The LDD lifecycle has four stages:

  • Egg Mass Stage (Late August to early May)
  • Caterpillar Stage (Early May to mid-July) 
  • Pupa Stage (Mid-July to early August) 
  • Moth Stage (Late July to mid and late August) 

The timing of each stage depends on climate and location.

 LDD Caterpillar Life Cycle

 

How to identify LDD

LDD Caterpillars:

  • 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)

Egg Masses:

  • Covered in tan-coloured hairs
  • Found on tree trunks or bark
  • Large egg masses are about the size of a loonie and may contain up to 1,000 eggs. The larger the mass, the larger the infestation.

LDD Caterpillar

Protect your trees

LDD caterpillars eat leaves causing trees to lose some or in extreme cases, all of their canopy. Long term effects can be reduced or prevented through management techniques. If you see small black caterpillars on your trees, here is how you can help protect them. Majority of caterpillars will be up to 1 inch in length at this time.

  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 material will work as well. Please avoid using tape as it could catch and harm other animals and insects unintentionally. Also the tape will need replaced as the stickiness wears down and it leads to unnecessary waste.
  2. Tightly tie a piece of string around the middle of the burlap piece. This will help prevent LDD from travelling up the tree trunk and remain underneath the burlap. 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 ring/ tent-like structure. Caterpillars will seek refuge under the burlap bands, and will not continue up the tree to the canopy.
  4. Check your burlap trap daily, to ensure no other animals get trapped and also to control LDD numbers. Remove the caterpillars and place them in soapy water for 1 to 2 days. Be sure to check the base of the burlap too. After the 1-2 days, the caterpillars can be removed from water and placed in the green bin.

Wear long sleeves and gloves as the LDD caterpillar hairs may cause skin irritation. It is also recommended that you change your clothing and wash them after this process in case any caterpillar hairs remain on your clothes.

LDD FAQs / Burlap Installation Fact Sheet 

What can residents do?

Property owners are responsible for managing trees (and pests) on their property. Residents are encouraged to inspect their trees and take action to remove LDD eggs masses, which will help reduce the risk of infestation. The below chart has various pest management options that residents may use to control the impact of LDD at home:

April to May

  • Prior to caterpillars hatching in early spring, egg masses can be scraped off trees and destroyed by placing them in a bucket of soapy water for a day or two
  • This will help reduce numbers of caterpillars hatching and defoliating the trees

April to June

  • If trees are severely infested (many egg masses are visible), an 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 may require more than one treatment; if an opportunity to treat trees is missed this year, homeowners may want to reserve a spot

May to August

  • In the spring and into the summer, caterpillars can be handpicked
  • To trap caterpillars (making them easier to collect), wrap burlap around the tree’s trunk at chest height, secure with a string or rope in the centre and fold the top half over the bottom half to form a bit of a ring; the caterpillars will seek refuge under the burlap bands, which can be checked regularly
  • Caterpillars can be removed and disposed of by placing them in bucket of soapy water for a day or two

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:

Before removal, wear gloves when handling caterpillars and egg masses to avoid an allergic reaction.

Egg mass removal steps

LDD Egg Masses on Tree

If your trees have been effected by LDD moths you may notice egg masses starting to form on your trees. To help prevent future damage follow these steps to remove egg masses:

  • Place your catchment container below the egg mass.
  • Use a 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.
  • Empty the contents of your catchment container or bag into a bucket of soapy water.
  • Leave the eggs sitting in the bucket for a day or two, then dispose of the contents in your green bin.

What is the Town doing?

The Town is monitoring trees in hotspot locations throughout EG and is part of York Region’s Invasive Species Technical Working Group. At this time, no municipalities are spraying, as the sprays may cause harm or kill other species that are helpful to our wider ecosystem. 

The Town is also preparing for a late/summer/early fall workshop/demonstration to showcase how to remove egg masses to help limit the spread next summer.

The Town also has a healthy population of NPV, the virus that kills the caterpillars, present in the Tall Pines, Donaldson, Artesian area! They will be working with the LSRCA to manually spread the virus to the Anchor Park Conservation Area within the next day or two. The virus is host specific and will only be harmful to the LDD species. It will not affect the trees, pets or people.

Roads and Sidewalks

The Town brought in their Operations team, using the sidewalk plow/sweeper and road flusher, to assist in dealing with the abundance of caterpillars and debris on the ground in heavily impacted areas.

The road flushing along the centerline and sweeping the sidewalks was effective and has been completed. This will also help prevent any flooding in the areas due to leaf and caterpillar debris covering catch basins. Roads and sidewalks will continue to be monitored for additional cleanup needed.

Frequently Asked Questions

Where did LDD's come from?
This invasive species was introduced to the United States in the late 1800s and was first detected in Ontario in 1969.
Why are LDD's harmful?
They are most destructive in their caterpillar stage as they will strip away foliage from a large variety of trees by eating the leaves. Most healthy trees can regrow their leaves but oak tree species are vulnerable and susceptible to repeated LDD feedings. Repeated defoliation can cause a large amount of stress to the tree which can kill it. There are things residents can do to help protect the health of their trees.
How can I identify that I have LDD's on my tree(s)?
Check for egg masses that are oval in shape and appear to be covered in tan-coloured hair. Once hatched the small black caterpillars may be around the egg sack.
Will LDD's harm my tree(s)?
Depending on the type of tree(s), LDD caterpillars can cause defoliation. Most healthy trees can regrow their leaves, but species such as Oak, are very vulnerable to LDD caterpillars and can be damaged over time and repeated infestations. Watering and fertilizing defoliated trees will help them overcome the stress and strain of growing another set of leaves. Factors such as drought will make the tree(s) more susceptible to die. There are things residents can do to help protect the health of their trees.
What types of trees are affected most?
 LDD caterpillars will eat the leaves on most tree types, but Oak trees tend to be favoured.
Where can I purchase Burlap?

Burlap can be purchased at most local hardware stores:

  • Home Depot
  • Home Hardware
  • Walmart
  • Canadian Tire 
Why won't the town treat my tree located on private property?
Trees located on private property are the responsibility of the homeowner. If you need assistance, it is recommended that you contact a licensed tree care company or specialist. There are also things residents can do to help protect their trees.
 I have an itchy rash. Do LDD bite or sting?

LDD caterpillars do not bite or sting, but many people have an allergic reaction from coming into contact with LDD. This bite like rash being experienced by some 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.

Will LDD be back again next year?
LDD outbreaks can last one to two years. Based on estimated populations from 2019 and 2020 (egg mass surveys), these numbers could repeat again next year (2022). A defoliation survey (July) and an egg masses survey (Fall) will be conducted to help make 2022 predictions about the LDD population.
Do LDD have natural enemies?

Squirrels, chipmunks, raccoons, skunks, multiple species of birds and native insects, as well as a naturally occurring fungus (not dangerous to humans) called Entomophaga Maimaiga help to reduce the population of LDD when it increases to high levels in particular areas.