Lymantria dispar dispar (Gypsy Moth)

The City’s 2021 LDD (Gypsy Moth) Management Program is now complete.

Brown moth on tree bark​Lymantria dispar dispar (LDD) is an insect native to Europe that has been introduced to North America. They are also known by the name gypsy moth. LDD caterpillars eat leaves from trees during the spring and early summer. This causes trees to lose their leaves.

Healthy trees can grow their leaves back in the same season, but an ongoing LDD infestation weakens trees and can make them more likely to be damaged from other insects.

How to spot an infestation

LDD like to eat the leaves on trees while they are in their caterpillar stage. They strip the leaves until early summer, when they enter their moth stage.

They prefer Oak trees but will eat the leaves of any hardwood tree such as oak, ash, birch or elm. Look for trees with many caterpillars and not a lot of leaf coverage.

What we are doing

The City monitors and controls LDD populations. Each year, priority areas are identified where there are high numbers of LDD. City-owned trees in these areas will receive treatments that may include:

  • Egg mass surveys during fall and winter months to help estimate population levels next year
  • Scraping egg masses off infected trees and killing the eggs
  • Wrapping burlap around trees to capture caterpillars
  • Hanging traps in trees to catch male Gypsy Moths and prevent them from mating
  • Tree injections of TreeAzin® a botanical injectable insecticide
  • Ground or aerial sprays

What you can do

Report sightings of LDD in your neighbourhood using our online reporting form. You can also check other sightings using our interactive map:

See interactive map Report LDD

You can also use some of these pest control techniques, to help protect trees on your property:

  • Remove caterpillars from tree trunks and soak in soapy water (most effective May-July)
  • Install burlap wrap to catch caterpillars before you remove and kill them (most effective May-September)
  • Install pheromone traps to confuse male moths (most effective June-August)
  • Search for egg masses to remove and destroy (most effective August-May)

Tree pest management updates

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Contact us

For more information about tree pests, email or call 311 (905-615-4311 from outside Mississauga).