Lymantria Dispar Dispar (LDD) moth (European Gypsy 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 maples, birches, and beeches, among other species.
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.
2021 was 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. Acting now will help reduce next year’s population levels.
Review the news release.
Based on population surveys conducted in 2020, Oakville faced extreme levels of LDD moth infestation in 2021 that could affect 102 hectares (252 acres) of town woodlands, resulting in a significant loss of trees if no action was taken.
The town conducted an aerial spray application of the safe biopesticide Bacillus thuringiensis Kurstaki (BtK) in spring 2021, to control LDD moth infestation in 15 town woodlands. Two treatments were performed by helicopter within a few days of each other. The first aerial spray was completed successfully on Thursday, May 27 and the second on Monday, June 7.
Additional ground spraying was also completed during the same period to target town trees adjacent to woodlands that had been identified as high-risk for LDD moth presence.
Please review our Frequently Asked Questions section for more information. If you have additional questions or concerns regarding LDD moth, please contact ServiceOakville at 905-845-6601 or email@example.com.
Here’s what you can do to protect your trees and help control the spread:
For detailed control tips, review the Health Canada Pest Control page.
Municipalities across Canada have conducted aerial spray programs in urban settings for decades.
The use of BtK is approved by the Health Canada Pest Management Regulatory Agency and is permitted under Oakville's pesticide-bylaw. It has replaced chemical insecticides in aerial spraying programs worldwide. According to Health Canada, BtK poses no threat to human health through either handling products directly or being exposed to them indirectly during a spray program.
Research shows that BtK used in aerial spray programs has no negative environmental or human health effects. BtK is a bacteria which occurs naturally in soil. The bacteria is 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. Learn more about BtK on Health Canada's Btk Fact Sheet (pdf) and on Natural Resources Canada's website.
LDD moth (sometimes called European Gypsy Moth) is an exotic forest insect pest that is native to Europe and considered to be a serious defoliator of trees and shrubs. After severe or repeated defoliation (loss of leaves), trees can die or become so weakened that they are vulnerable to secondary infestations.
LDD moth caterpillars typically begin to emerge at the end of May. They continue to feed on leaves and grow for about 6 to 8 weeks. They then pupate at the end of June. After turning into moths, they are active for about 2 to 3 weeks, looking for an ideal place to lay an egg mass to start the cycle anew the subsequent year..
According to the town's 2016 iTree Report, LDD moths, if left untreated, have the potential to impact 409,000 trees in the town of Oakville. This is equal to 23 per cent of the town’s tree canopy. While the moth stage of the LDD moth does not feed on trees, the caterpillar stage of this insect can potentially devour every leaf of the tree’s canopy. They are capable of causing a considerable amount of damage to trees during an extreme infestation. The severity of the tree damage depends on the degree of infestation, past defoliations and the current health of the tree. If a tree has been weakened by previous defoliations or stressed by other conditions such as drought and attacks from other insects the defoliation can lead to the death of the tree.
All species of oak are susceptible to LDD moth. The larva of this insect also feed on 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.
Yes. At normal population levels, LDD moths play a crucial role as a food supply for many of the native species of birds that live in Oakville’s urban forest, as well as other woodland animals such as raccoons. Usually, diseases caused by bacteria, fungi or viruses contribute the most to keeping LDD moth levels low.
The town's Urban Forestry section is responsible for the maintenance of town trees only.
There are many ways private tree owners can protect their trees from LDD moth. Contact a certified tree service provider for information on treatment options or review the What You Can Do section on this page or Health Canada's Gypsy Moth Fact Sheet.
Most insects are a nuisance only and under normal circumstances do not require a control program. Visit our Invasive Species page to learn more.
Forestry staff has been monitoring the population of LDD moth since 2002. In 2005, staff observed an increase in gypsy 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.
Based on population surveys conducted in 2017, Oakville faced extreme levels of gypsy moth infestation in 2018 that could have affected 110 hectares (272 acres) of town woodlands and resulted in a significant loss of trees if no action was taken.
In spring 2018, 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.