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Invasive Insects and Plants

There are many different invasive insects and diseases that can have devastating effects on the health of the county’s forests.

On this page

Oak Wilt

Oak Wilt (Bretziella fagacearum) is a non-native fungus that infects and kills all species of Oak. Trees in the Red Oak group (Red Oak, Black Oak, and Pin Oak) are the most susceptible and can be killed in as little as two to six weeks. Trees in the White Oak group (White Oak and Bur Oak) are more resilient and it usually takes one to two years before the tree dies.

Oak wilt is spread by sap beetles that carry the oak wilt fungal spores on their bodies from infected trees to healthy ones as they move around in search of food.

  • Leaves begin to discolour, appearing lighter in colour, yellow or brown.
  • Leaves towards the top of the tree and branch tips begin to wilt or brown.
  • Leaves begin to drop early, starting in the summer
  • Vertical cracks appear in the bark with and underlying sweet-scented fungus

There is currently no cure available for trees infected with Oak Wilt. The best approach is to monitor for signs and symptoms to reduce the risk of trees becoming infected:

  • Report suspected Oak Wilt sightings to the Canadian Food Inspection Agency (CFIA).
  • Do not move firewood or other wood products.
  • Avoid pruning or removing Oak trees from March to September when the fungus is most active.
  • If you must prune or move during the active period, cover the entire exposed area of the pruning cut or stump with paint to prevent fungus from being able to enter the tree.

Hemlock Woolly Adelgid

Hemlock Woolly Adelgid (Adelges tsugae) is an invasive species of aphid-like insect that attacks and kills hemlock trees. Infestations can kill a healthy Hemlock in four to fifteen years.

It is most commonly spread by wind, birds, and deer, but it can also be spread through the movement of firewood and wood products.

  • Small white sacs form at the base of the needles.
  • Buds and branches near the top of the trees die back and may break off.
  • Needles may begin to drop early in the season.
  • Needles may turn a grayish-green colour rather than healthy, shiny, dark green.

  • Report suspected Hemlock Woolly Adelgid sightings to the Canadian Food Inspection Agency (CFIA).
  • Do not move firewood or wood products.
  • Do not hang bird feeders on Hemlocks or trees in the surrounding area.

Emerald Ash Borer

The Emerald Ash Borer (EAB) is a non-native beetle that lives in ash trees and lays eggs on the bark and bark crevices. The larvae then tunnel beneath the bark and feed on the layer of live cells between the bark and the sapwood, cutting off nutrients and water to the upper portions of the tree.

  • The leaves in the top third of the ash tree lose their green colour, thin and die back.
  • New branches begin to grow from the low trunk or roots.
  • White lines or canals are evident under the tree's bark.
  • The bark begins to split.
  • There are small D-shaped holes in the bark.
  • Increased woodpecker activity on the tree resulting in large holes.

  • If you have an ash tree on your private property, contact a Certified Arborist to inspect your tree to confirm the presence of EAB and to recommend treatment options.
  • If you have Ash trees in your woodlot contact the Facilities and Parks Operations division to determine if insecticides or removal is needed.

Learn more about Emerald Ash Borer from the Canadian Food Inspection Agency.

Spongy Moth

The spongy moth (Lymantria dispar dispar) is an invasive species introduced to Canada and the United States in the mid-1800s. Spongy Moth caterpillars feed primarily on Oak species but may also damage Maple, Alder, Birch, Hawthorn, Beech, Crabapple, Poplar, Cherry, Willow, Basswood and others.

Spongy moth populations tend to be cyclical, with peaks every 7 to 10 years, followed by a dramatic population decline of the pest. During years with low populations, the feeding caused by the caterpillars is barely noticeable and healthy trees that are defoliated are able to grow new leaves and will recover the following year. 

  • Masses of moth eggs are visible on tree bark, branches or other projected places
  • Tree leaves begin to defoliate, starting with small holes and then the whole leaf

  • For single trees or small groups, the installation of sticky bands will catch the caterpillars as they move along the trunk of the trees.  Pheromone traps can also be used to lure and trap male moths, preventing them from mating with female moths is another effective control.
  • For woodlands or large areas, an aerial spray can be highly effective at reducing Spongy Moth populations in the local area, but won’t have a significant impact on populations outside of the control area. The chemical controls for Spongy Moth are comprised of the bacteria Bacillus thuringiensis (Bt) already found in the local environment that kills the Spongy Moth larvae quickly.
  • Haldimand County does not administer an aerial spray program for the control of Spongy Moth on public or private lands. If you are concerned about Spongy Moth on your private property, you can contact a Certified Pesticide Exterminator to inspect your trees.

Learn more about the spongy moth from the Canadian Food Inspection Agency.

Contact Us

Forestry
53 Thorburn Street South
Cayuga, Ontario
Canada, N0A 1E0

Email Forestry
Phone: 905-318-5932, ext. 6503

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