Invasive Species

Invasive Species are organisms (plant, animal, fungus or bacterium) that are not native to a region and have negative effects its economy, environment or public health. Emerald Ash Borer (EAB) and LDD Moth are two invasive species found in Northumberland County.

Tree showing EAB damage

Emerald Ash Borer

The EAB is an invasive insect that bores holes in ash trees and kills them within two years. The larvae feed on the inner bark of the tree, removing the bark and disrupting the flow of nutrients. This results in the death of the tree by girdling.

EAB was first located in Michigan in 2002. It has now spread throughout Ontario, Quebec and the eastern United States. The insect can travel short distances through flight but primarily moves through human assistance (firewood, nursery stock and wood products).

Frequently asked questions

What are we doing about EAB?

Northumberland County is responsible for treating or removing and replacing ash trees located on County roads and other County-owned properties. Infected trees pose a hazard of falling due to weakened, damaged bark. In 2016, we inventoried all ash trees along County roads and on County properties. The scheduled removal of these ash trees began in 2018. 

How many trees are being removed in my area?

Please review our map, which outlines the number of ash trees to be removed by section of road.

Will downed trees be replaced?

The County is partnering with Lower Trent Conservation on a program to make saplings available to Northumberland residents to plant on their properties, at no cost. This program will subsidize 12,000 trees annually (60,000 trees overall), or approximately 10 replacement trees for every one tree being removed.

Applications to receive free saplings will be available on the Lower Trent Conservation website. Trees will be distributed in the spring.

Applications for spring 2021 have now closed. Stay tuned for information about applications for spring 2022.

What to do if you have ash on your property?

Property owners are responsible for maintaining, treating and removing ash trees (and any other trees) located on their property. Dead and dying trees are hazardous and must be removed.

Ask a professional arborist for:

  • Proof of liability insurance
  • Proof of WSIB
  • Certification in good standing with the International Society of Arboriculture

If you choose to treat your ash tree with insecticide, ask for a pesticide applicators license.

Before removing your tree, check to see if your municipality has a tree by-law in place.

LDD Moth

Lymantria dispar dispar (LDD) is an invasive moth that was first detected in Ontario in 1969. The lifecycle of LDD includes: egg masses, caterpillar (larva), pupa and adult moth.

Graphic depicting the lifecycle of the LLD: Egg stage is from September to April, caterpillar stages from end of April to end of June, Pupa stage in mid summer, moth stage from July to August. Egg masses should be destroyed in february, burlap banding completed in may, pesticide can be used in May or June and hand picking can be completed in June/July.

Frequently asked questions

What does LDD look like?

Photo of gypsy moth egg masses
Stage 1 - Egg masses

Egg masses are about 4 cm, tan-coloured, and can be found on any hard surface – including tree trunks, furniture, and buildings.

Photo credit: Milan Zubrik, Forest Research Institute – Slovakia, Bugwood website


Photo of gypsy moth caterpillar
Stage 2 - Caterpillars

Caterpillars are 5-6 cm long and have 5 pairs of blue dots and 6 pairs of red dots along their backs.

Photo credit: Connecticut Agricultural Experiment Station, Connecticut Agricultural Experiment Station, Bugwood website


Photo of gypsy moth pupa
Stage 3 - Pupa

Pupa are 3 cm long, brown with small white/yellow sparse hairs, and can be found in cracks of trees and building overhangs.

Photo credit: Jim Occi, BugPics, Bugwood website 


Photo of gypsy moth adult
Stage 4 - Adult moths

Adult moths can be white with dark markings (females, 5 cm wingspan) or brown with dark markings (males, 2.5 cm wingspan).

Photo credit: Hannes Lemme, Bavarian State Research Center for Agriculture, Bugwood website

What does LDD eat?

LDD caterpillars defoliate leaves of host trees, mostly hardwood species, such as oak, birch, poplar, willow, maple and others.

How can I protect my trees?

Property owners are responsible for managing trees and pests on their property.

Tree damage from LDD depends on the degree of infestation, past defoliations, the tree's vulnerability and the environment. Damage levels can range from light to almost complete defoliation. Healthy trees often recover from defoliation, however draught or disease stressed trees can be further weakened and potentially die. Severe defoliation of coniferous trees may result in mortality after just one season. Maintaining healthy trees and forests is an important defence against LDD.​

Help stop the spread of LDD by making sure not to move firewood.

Removing egg masses

Egg masses can be removed from trees in fall and winter by soaking the eggs in a soap and water mixture.

Removing caterpillars

A band of burlap or other cloth product wrapped around the trunk will provide a place for caterpillars to hide during the heat of the day. Check these bands regularly and scrape caterpillars into a container of soapy water to remove them.

What causes an LDD outbreak?

Outbreaks of this species are cyclical with population surges approximately every 7-10 years. Outbreaks are caused by biological and environmental factors such as warm winters and dryness in spring. Naturally occurring viral and fungal pathogens will control populations and collapse the population back to low densities within 1-3 years of outbreak.

What are we doing to combat LDD?

Northumberland County is taking an Integrated Pest Management (IPM) approach. This means we are using different effective and environmentally sound management techniques to address the pest population, starting with the least invasive options.

Surveys were completed in fall 2020 to assess the population and forecast future impacts of LDD. Further monitoring is planned for 2021. It is anticipated that some areas within the County will see moderate to severe defoliation in 2021.

County staff have also been removing egg masses from the Northumberland County Forest in Special Management Zones to help protect areas with high conservation values.

At the June 16, 2021 meeting of Northumberland County Council, Forest staff delivered an update to Council on LDD in Northumberland.

Why is Northumberland County not using pesticides to combat LDD? 

We have decided not to do aerial spraying at this time. In monitoring the defoliation from the 2020 outbreak, the County determined that the vast majority of trees fully recovered, despite their stark appearance as a result of defoliation. Given the majority of trees do recover, and the fact that spraying kills other threatened caterpillars that play a crucial role in the food chain of a forest ecosystem, it is not an option we are pursuing at this time.

We will be monitoring the situation again this year and, while spraying is not being widely used in other communities at this time, we will be examining the effectiveness of any spraying that is done  to determine whether any change in approach is required for 2022.

Where can I get more information?

To contact a Certified Arborist or Professional Forester, please visit: