Hemlock woolly adelgid Adelges tsugae (Annand) is an aphid-like insect that attacks and kills hemlock trees by feeding on nutrient and water storage cells at the base of needles.
This pest is a serious ecological threat. In many forests across Canada, hemlock serves a vital role in protecting watersheds and streams in natural forest ecosystems. Loss of eastern hemlock could negatively affect the health of vegetation, birds, aquatic organisms and mammals.
What you can do
- Don't move firewood: buy local or kiln dried firewood to avoid spreading plant pests to new areas
- Know which areas and items are regulated for hemlock woolly adelgid in Canada
- Look for signs in the hemlock trees around you and report suspected sightings immediately:
Report a hemlock woolly adelgid sighting
How to spot it
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Branch with egg sacks -
Close up of egg sack with insect -
Forest affected by hemlock woolly adelgid
Its egg sacs, which look like cotton balls or clumps of snow, can be found at the base of needles. Look for:
- white "woolly" sacs resembling tiny cotton swab ends at the base of hemlock needles on young twigs; these are most obvious in the spring
- premature bud and shoot dieback
- premature needle loss
- thinner, greyish-green crown (healthy crowns are a shiny, dark green colour)
- dieback of twigs and branches
- discoloured foliage
- tree death within 4 to 15 years
Where it is
The areas regulated for hemlock woolly adelgid in Canada are:
- the province of British Columbia
- Digby, Queens, Shelburne, Yarmouth, Annapolis, Kings and Lunenburg counties in Nova Scotia
- the Regional Municipality of Niagara, Haldimand County, the City of Hamilton, the Township of Alnwick/Haldimand.
Learn more about detections and regulated areas and items for hemlock woolly adelgid in Canada.
How it spreads
It can be spread by wind, animals, and human movement of nursery stock, logs, and other wood products.
What we are doing
Import and domestic movement requirements are in place to prevent the introduction and minimize the spread of the hemlock woolly adelgid. To see the complete program, please refer to D-07-05: Phytosanitary Requirements to Prevent the Introduction and Spread of the Hemlock Woolly Adelgid (Adelges tsugae Annand) from the United States and within Canada.