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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 gypsy 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 gypsy moth can be controlled with an effective Integrated Pest Management (IPM) plan.
The town continues to track gypsy moth populations and new outbreaks. By the summer months gypsy moth have pupated and laid their eggs. Surveys of egg masses are conducted to predict population levels the following year, and inform management actions that may need to be taken.
Based on population surveys conducted in 2020, Oakville faces extreme levels of gypsy moth infestation in 2021 that could affect 102 hectares (252 acres) of town woodlands, resulting in a significant loss of trees if no action is taken.
The town will be conducting an aerial spray application of the safe and naturally occurring insecticide Bacillus thuringiensis Kurstaki (BtK) this spring to control gypsy moth infestation in 15 town woodlands. Two treatments will be performed by helicopter within a few days of each other between May 1 and June 15, 2021, weather permitting, from 5 – 8 a.m. Dates and more specific details will be posted here as they become available. In order to monitor the specific time that gypsy moth caterpillars emerge in 2021, which is needed to plan the best time to initiate the aerial spray, the town has identified one sample oak tree in four woodlands highly impacted by gypsy moth -- Colonel William Woods, Settler Woods, Winston Woods and Morrison Valley Woods. The sample trees are marked with pink flagging tape around the trunk of the tree and a pink dot at the base.
If you live in the near vicinity of any of the town woodlands that will be treated in the 2021 gypsy moth aerial spray program and would like to be receive email notification prior to its occurrence (48 hours), please provide your contact information including home address, to firstname.lastname@example.org. Your email will be saved in our records for the exclusive digital notification regarding this year’s aerial spray.
Please review our Frequently Asked Questions section for more information. If you have additional questions or concerns regarding gypsy 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 Gypsy Moth 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.
Gypsy moth (Lymantria dispar dispar) 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.
Gypsy 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, gypsy 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 gypsy 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 gypsy 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, gypsy 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 gypsy 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 gypsy moth and cankerworm. 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 gypsy 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 gypsy 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 gypsy moth infestation which successfully conserved a significant portion of Oakville’s tree canopy.