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.
Here’s what you can do to protect your trees and help control the spread on your own property:
For detailed control tips, review the Health Canada Pest Control page.
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. For details, review the April 28, 2022 news release and visit the aerial spray map for woodlands included in the 2022 aerial spray program.
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.
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.
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.
If you have additional questions or concerns regarding LDD moth, please contact ServiceOakville at 905-845-6601 or firstname.lastname@example.org.
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.
Forestry staff have been monitoring the population of LDD moth since 2002. In 2005, staff observed an increase in LDD moth population, and undertook a more comprehensive monitoring program.
As a result of a population increase in 2007, Oakville participated in a collaborative spray program in 2008 with neighbouring municipalities to spray 63 hectares (155 acres) of municipally infested woodlands with the insecticide Btk. The aerial spray program was considered a success. The LDD moth population in the following years was negligible and an integrated pest management approach that did not require aerial spraying was implemented. Forestry staff manually removed egg masses from the trees, where possible, prior to spring emergence.
The 2012 and 2013 egg mass surveys reported a slight increase in population levels. High infestation levels were localized, and protective injection treatments were implemented in select hot-spot locations from 2013-2017.
In spring 2018 and 2021, the town completed an aerial spray in select town woodlands to control the LDD moth infestation which successfully conserved a significant portion of Oakville’s tree canopy.