What are they?

Lymantria Dispar Dispar (LDD) moth (also known as European Gypsy Moth or Spongy Moth) is a non-native insect that is considered a major destructive pest in North America. When populations are high, they can eat all the leaves on a tree in a short amount of time. When leaves are lost in successive years, trees can die.

All species of oak are susceptible to LDD moth. This is of particular concern as oaks are high-value heritage trees of immense significance to Oakville’s landscape and neighbourhoods. They also target poplar, birch, willow, maple, beech, and cherry and if faced with a shortage of deciduous leaves, they will feed on conifers (hemlock, pine and spruce) and ornamental shrubs.

What you can do

Here’s what you can do to protect your trees and help control the spread on your own property:

  • In the summer and fall, physically remove LDD moth egg masses. Use a putty knife or trowel to scrap eggs into a container and destroy the eggs by leaving them in soapy water for several days.
  • In the spring, apply sticky bands or burlap around trees to trap emerging LDD moth caterpillars. Commercial sticky bands can be found at most home and garden stores.
  • Use gloves to hand-pick caterpillars and crush them or place them in a bucket of soapy water.
  • Contact a professional tree care service provider to discuss spraying.

For detailed control tips, review the Health Canada Pest Control page.

What the town is doing

The results of the egg mass surveys indicate that the outbreak level will be light or nonexistent across the town in 2023, with no woodlands forecasted to experience heavy or severe defoliation. As such, an aerial spray program will not be conducted in 2023 for the treatment of LDD moth. 

If you have additional questions or concerns regarding LDD moth, or a question regarding a town tree please contact ServiceOakville at 905-845-6601 or service@oakville.ca

The Town of Oakville is continuing to monitor the results of the aerial spray and the possible next generation of Lymantria Dispar Dispar (LDD) moth infestation for spring 2023. 

Egg mass surveys are conducted to estimate the subsequent year’s outbreak level. The town’s response will be based depending on the results of the surveys.

Based on LDD moth population surveys conducted in 2021, the town expected high infestation levels in the spring of 2022. An anticipated 358 hectares (885 acres) of town woodlands would have experienced heavy to severe defoliation (loss of leaves) if no action was taken. 

A low-flying helicopter was used to administer a safe and naturally occurring insecticide over the designated town woodlands. A second spray was conducted within a week of the first in order to control the invasive moth’s caterpillars which, if left unchecked, can kill trees at an alarming rate. 

Residents who lived in the near vicinity of any of the town woodlands that were treated were notified that they could sign up to receive an email notification 48-hours before the spray.

The 2022 aerial spray followed the 2021 and 2018 aerial spray programs with two applications of bioinsecticide Bacillus thuringiensis kurstaki (Btk) applied by helicopter, approximately 3-10 days apart. 

BtK has no negative environmental or human health effects. The bacteria occur naturally in soil and are poisonous only to a certain group of insects when ingested during their larvae or caterpillar stage. BtK does not affect adult moths or butterflies or other beneficial insects such as honeybees, or pets, birds, fish, or mammals.

  • May 30, 2022: The first aerial spray was completed successfully. A second spray will be necessary within one or two weeks (weather permitting).
  • June 3, 2022: The second and final aerial spray was successfully completed on June 3, 2022.

The designated woodlands and trails were closed temporarily during the spray and reopened immediately after. Aerial spraying did not take place over town streets or residential properties. No special precautions were required for residents near the spray areas. 

Additional ground spraying was completed at the same time to target town trees adjacent to woodlands that had been identified as high-risk for LDD moth.

Visit the aerial spray map for woodlands included in the 2022 aerial spray program.

The damaging effects of LDD moth can be controlled with an effective Integrated Pest Management (IPM) plan.

In August 2021, Oakville Town Council approved funding to remove LDD egg masses from 2,300 municipal street trees in the fall. 

That year saw one of the highest recorded populations of LDD moth in the province in the last 30 years. According to the latest defoliation and egg mass survey conducted by the town, there are areas of concern that could see another year of heavy LDD infestation in 2022. 

For more information, review the August 10, 2021 news release.