Invasive Species Centre
HWA egg masses on Eastern hemlock twig underside.
The presence of the Hemlock Woolly Adelgid (HWA) was confirmed in the Town of Lincoln between Grimsby and St. Catharines. This invasive forest insect, originally from Eastern Asia, poses a significant threat to the health of hemlock and spruce trees.
The HWA, first identified in Virginia in the 1950s, has since spread across North America, causing branch dieback and tree mortality. With potential impacts on forest ecosystems, wildlife habitats, and outdoor recreation, it is crucial for community members to be proactive in addressing this issue.
The Hemlock Woolly Adelgid relies on Eastern hemlock trees as their host, extracting sap from the base of the tree needles. This feeding behaviour leads to branch dieback, premature bud and shoots dieback, needle loss, and the eventual death of the tree within 4 to 15 years.
If left unmanaged, this invasive pest can severely disrupt forest ecosystems, impacting the health of forest rivers and streams. Furthermore, the presence of HWA may also have negative implications for outdoor recreation in parks and other urban green spaces.
The Hemlock Woolly Adelgid (HWA) can spread through various means. The primary mode of spread is through the wind, as air currents can carry the insects. They can also be transported by moving infested plant material like branches or cuttings.
Additionally, HWA can be accidentally transported by humans, animals, or birds that come into contact with infested trees or areas.
What Can Community Members Do?
Community members and property owners play a vital role in managing the spread of HWA. It is essential to be vigilant and look out for signs and symptoms of infestation, which include:
- White "woolly" sacs resembling tiny cotton swab ends at the base of hemlock needles on young twigs (most evident 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
- Discolored foliage
- Death of the tree within 4 to 15 years
When accessing natural areas, it is essential to check and remove any plant material and debris from clothing, equipment, and pets to minimize the risk of spreading HWA. Staying on designated trails can also reduce the chance of encountering and disturbing infested trees.
Additionally, avoiding placing bird feeders near hemlock trees is advised, as birds can inadvertently spread HWA to new locations.
Reporting Infestations
If an infestation is suspected, it is vital to report it to the Canadian Food Inspection Agency (CFIA). Providing an accurate location of the suspect tree and submitting photos of the symptoms will aid the CFIA's response.
They may conduct site surveys and collect samples to assess the severity of the infestation and take appropriate action.
