Invasive Species

The term invasive species refers to any non-native species that is introduced to an area where they cause or are likely to cause significant damage to the environment or other existing species.

Many invasive species are introduced to these areas accidentally and can have significant environmental and financial impacts if not controlled in a timely manner. This includes:

Loss of native plants and animals
Decreased native fish populations and size of fish
Loss of biodiversity
Transmission of harmful diseases
Increased risk of wildfires
Diversion of taxpayer dollars for clean-up and maintenance efforts
Loss of recreation spaces

Raising awareness is key in preventing the spread of these pests. Learn more about the invasive species that put Fredericton at risk and how you can do your part to prevent the spread.

Preventing the Spread

Invasive plants and animals spread in a variety of ways:

Dumping of garden debris into parks or wild areas
Planting invasive plants in the garden
Release of domestic pets
Not cleaning boats and aquatic equipment before going to another water body
Seeds can be transported by wind, water, animals, vehicles, equipment, and people

The New Brunswick Invasive Species Council is a non-profit organization that works diligently to prevent and manage the spread of invasive species throughout the province. They have outlined several actions to help protect our province from these harmful species:

Clean, Drain, Dry: Clean all equipment and watercrafts with hot water, inspect for plant matter or mud, drain all compartments of water and dry all equipment before and after entering a new body of water.

Play, Clean, Go: Clean off your footwear, equipment, tires, pets, and anything you bring outdoors before and after visiting a new area.

Buy Local, Burn Local: Buy local firewood near your location and leave leftover firewood on site. Forest pests are easily moved through firewood and can destroy city forests and urban trees.

Don’t Let It Loose: Never release pets, pond or garden plants, live food or non-native bait into waterbodies or greenspaces where they do not belong.

Plant Wise: Only plant native species in your garden and inspect plants thoroughly for invasive pests before planting. Read the Grow Me Instead Guide to learn what native alternatives exist to replace harmful and invasive horticultural plants.

NOTE: Do not put invasive plants (whole, cuttings, or seed heads) or infected ash tree limbs in your backyard compost or in the City yard waste collection.

Invasive Species Present in Fredericton

Dog-Strangling Vine

A member of the milkweed family, Dog-strangling Vine (DSV) spreads along the ground and twines around other plants and trees, forming dense patches that outcompete native plants, interfere with infrastructure like utility corridors, and hinder forestry and agricultural operations. DSV also impacts endangered Monarch Butterfly populations as the butterflies will mistakenly lay their eggs on this plant instead of native milkweed, but once hatched the caterpillars cannot feed on DSV and die.

Emerald Ash Borer

Unfortunately, the City’s tree canopy is under threat from an insect called the Emerald Ash Borer (EAB). It was first detected in Fredericton in February 2021. The City of Fredericton has written a management plan to minimize the impact.

Property owners have a role to play, too. They can monitor ash trees on their own properties and follow the management plan as outlined.

Credit: Marianne Prue, Ohio Department of Natural Resources - Division of Forestry, Bugwood.org

Management Plan

Detect - City staff continue to work with provincial, federal, and private sector representatives to detect the insect’s presence in the City of Fredericton.

Treat - Select City trees will be identified for treatment. This is not a long-term solution, however, and it is not available for all ash trees on City property due to the expensive nature of the treatment. Homeowners may choose to treat their ash trees.

Remove - Removal of ash trees will be necessary to control the spread and minimize the risk to public safety. Neighbourhoods with a large ash proportion will be impacted greatly.

Replant - Staggered removal and replanting of trees, over several years, will result in the least impact on the City’s tree canopy and create a more disease resistant urban forest.

If you are wondering if your tree is infested with the Emerald Ash Borer or would like more information, please visit the resources below:

Managing Emerald Ash Borer
Emerald Ash Borer (Government of Canada)
Frequently Asked Questions (PDF)

Eurasian Watermilfoil

Eurasian watermilfoil is threatening Canadian waterways by competing directly with native plants and reducing biodiversity. It can reduce the amount of oxygen within the ecosystem, making it difficult for other species to survive; and large, thick mats of Eurasian watermilfoil impact recreational activities such as swimming, boating, and fishing.

Garlic Mustard

Garlic Mustard, an edible garden herb, is an aggressive plant that forms dense stands in early spring, monopolizing resources and shading out native species. It is avoided by deer, who then over-browse native species, and is allelopathic - meaning it inhibits the growth of other plants around it by releasing biochemicals into the surrounding soil.

Giant Hogweed

Giant Hogweed is a very large flowering plant (up to 3 m/10 ft) that belongs to the carrot family. This invasive plant resembles Queen Anne’s Lace and was planted as an ornamental garden species. It can live for 5-7 years and is characterized by a large umbrella shaped head of white flowers that produces thousands of seeds per plant.

Giant Hogweed has a phytotoxic sap that can produce 3rd degree burns on skin when exposed to sunlight, so management of this plant requires caution. This invasive plant establishes rapidly on the roadsides and ditches and poses a human health risk when growing in public areas.

Use extreme caution when handling or removing this plant, and wear protective equipment as required. If you believe you have been exposed to Giant Hogweed sap, immediately wash the area with cold water and soap and remove from sunlight.

Glossy Buckthorn

Glossy Buckthorn is a deciduous shrub/small tree that is incredibly invasive along forest edges and open areas. This extreme proliferation, often aided by the spread of seeds by birds, blocks native species from growing, negatively impacting native plant and insect diversity and abundance.

Goldfish

Goldfish are a freshwater fish belonging to the carp family and are not native to New Brunswick or North America but have been released in ponds and lakes in Fredericton, including in Odell Park. They eat a variety of insects, crustaceans, and plants which allows them to grow quickly and compete with native fish species for both food sources and habitat. Goldfish have been introduced into our waterbodies primarily as discarded pets threatening the integrity of our natural ecosystems.

Japanese Barberry

Japanese Barberry is a common ornamental garden plant that can escape into nearby natural areas where it overtakes the understory, pushing out native species and reducing wildlife habitat. It can quickly spread through the expansion of its rooting system (rhizomes), broken or cut stems creating new sprouts, and seed dispersal by birds.

Japanese Knotweed

Japanese knotweed is an aggressive semi-woody perennial plant that was introduced as a horticultural plant to act as a “living fence”. It forms dense thickets of bamboo-like vegetation that outcompete native plants and negatively impacts wetland and riparian areas. Its aggressive growth habit also makes it a risk to infrastructure like roads and building foundations, as it will grow right through them. This invasive plant forms extremely long roots called rhizomes that can extend up to 2m deep. These make it almost impossible to eliminate entirely, meaning it will continue to grow back and spread beyond the area where it was originally planted. Japanese knotweed is heavily established in Fredericton, however, the City is managing knotweed in a few key areas.

Oriental Bittersweet

Oriental Bittersweet is a woody vine that is popular in gardens for its colorful berries that stay on through winter and its twining vines are often used for wreath making. It can overtake natural environments by shading and choking out native vegetation: even uprooting trees under the weight of its vines!

Phragmites/Common Reed

Phragmites is a type of perennial reed grass commonly found in wetlands, field edges, and along shorelines. Individual stems are tall (1–5m) and have large flowering seed heads and long slender leaves. When invasive Phragmites invades, it establishes rapidly and forms tall, dense monocultures that outcompete native plant species and reduce food and habitat for various wildlife species. Once the Phragmites dies, these monocultures of dead foliage can increase the risk of wildfire.

Woodland Angelica

This invasive plant can be found in wet and disturbed areas and is further distributed through flood events when plant seeds are washed downstream. Woodland Angelica is an aggressive invader and can rapidly establish itself in a wide variety of environments. Once established, it can outcompete native plant species and provide little benefit to local wildlife. Additionally, the sap of Woodland Angelica can cause a dermatitis type skin reaction. Use caution when cutting or managing this plant.

Invasive Species That Could be Coming Soon

Hemlock Woolly Adelgid

Hemlock Woolly Adelgid (HWA) is an aphid-like insect that attacks Eastern Hemlock trees, which make up a large part of the forest of Odell Park. It feeds on the base of hemlock needles, causing premature dieback, needle loss, foliage thinning, and tree death within 5-15 years. HWA is easily spread by the wind, birds, other wildlife, and by humans moving infested wood products. It is now in coastal Maine and southwestern Nova Scotia.

Oak Wilt

Oak wilt is a fungal disease that can kill a red oak within a single season. It is spread naturally through root grafts, the movement of infected wood, or beetles that can carry fungal spores. Oak wilt has only been found in regions of Ontario but could pose large threats to our forests if it reaches New Brunswick.

Spotted Lanternfly

Spotted Lanternflies are invasive insects that feed on plant sugars, disrupting the normal nutrient circulation in the plants causing degradation and death over time. They are known to feed on over 70 different plant species but prefer fruit and ornamental trees; this makes them a serious threat to wine and fruit industries. It has recently been sighted in southern Ontario.

Credit: NBISC 2025, Jason Ondreicka/Dreamstime.com

Zebra Mussels

Zebra Mussels are small, invasive freshwater mussels. They have recently been found in the Wolastoq (Saint John River) and as close as the Mactaquac head pond, and they are expected to reach Fredericton soon. Zebra Mussels are spread due to human activities like boating and by the natural flow of water downstream. They pose both environmental and economic threats.

Zebra Mussels can have significant impacts on freshwater ecosystems as well as the infrastructure and recreational activities that are dependent on these bodies of water.

They:

Outcompete native species
Change plant composition
Form incredibly dense colonies, which can clog pipes
Colonize watercraft, fishing gear, and docks
Can increase algal or cyanobacteria blooms
Sharp shells on beaches can cause cuts and injuries

How to Identify a Zebra Mussel:

Size: Small – average size of 2 – 2.5 cm.
Shell: Triangular shape with rounded bottom
Color: Zig-zag pattern either brown or white

To prevent the spread, ensure you clean all boats and equipment with hot water, drain any standing water, and allow it to dry before moving to another water body.

The City of Fredericton has developed a draft management plan to combat the introduction of Zebra Mussels. If you think you have found a Zebra Mussel, you can report a sighting by following the link below:

Learn how to identify different invasive species in New Brunswick

Learn more about prevention programs to help stop the spread

Report sightings of invasive species in New Brunswick