Pest known to destroy hemlocks makes first appearance in Nova Scotia

by Brittany Wentzell

  • <p>WIKIPEDIA PHOTO</p><p>The egg sacs of the Hemlock Woolly Adelgid look like small cotton balls and attach themselves to the bases of the needles on a hemlock tree.</p>

A destructive, invasive pest known to kill eastern hemlock trees has been found in Nova Scotia for the first time and is spreading.

"We had a detection of (Hemlock Woolly Adelgid) in mid-July and have since been doing survey work to determine the extent of the infestation in Nova Scotia," said Ron Neville, plant health survey biologist with the Canadian Food Inspection Agency (CFIA), which is in charge of regulating the invasive species.

The Hemlock Woolly Adelgid (HWA), is an aphid like insect that feeds on the nutrients of a hemlock tree at the base of the needles, sometimes injecting a toxin into the tree at the same time. The needles of the tree eventually turn a gray-green colour and trees can die three or four years after infestation though some die up to 10 years later.

Shelburne, Digby and Yarmouth counties have known infestations, while Queens and Annapolis counties have had some HWA sightings, particularly on the western side of the county where the infestation is starting to travel northeast.

"What people will see on an infested tree is the white wooly egg sac and these wooly egg sacs look like small cotton balls and they're at the base of the needles," said Neville. "Each sac can contain up to 200 eggs."

HWA first came to North America from Japan by accident in the 1950s, first landing in Virgina. Since then the pest has traveled throughout the eastern United States and has been found in southern Ontario and in British Columbia.

Damages done to the hemlock trees can affect the entire surrounding ecosystem says Neville.

"It has potential to create major ecological impact in Canada. In many forests hemlocks serve as a foundation tree for the environment ... it's ecosystem around it depends upon hemlock being present and loss of eastern hemlock could negatively impact the health of vegetation, birds, aquatic organisms and mammal," said Neville.

Hemlocks are also a common variety of tree found in Acadian forests and old growth forests in Nova Scotia.

The life cycle of HWA is such that it is only just starting to "wake up" now and will be active throughout fall, winter and spring. Once spring comes, the HWA working group, consisting of members from CFIA, Department of Natural Resources, Parks Canada and the Mersey Tobeatic Research Institute, will continue surveys and sampling to determine how much the pest has spread.

Neville says those groups, as well as industry partners, are trying to determine the best approaches to the situation as well. In the case of Ontario, the pest was found in a small number of trees so they were removed and destroyed, which led to the eradication of HWA in that instance.

"The HWA is regulated in Canada and the Canadian Food Inspection Agency has responsibility for the plant protection act and it's that legislation where the pest is regulated. It's regulated to protect Canada's forests and nurseries," said Neville.

"We have been working with our colleagues in the northeastern united states," he added. "They have efforts underway to manage HWA through a variety of measures using the introduction of bio controls, application of pesticides and some harvesting methods, so the suitability of these strategies needs to be assessed to see if they are suitable for Nova Scotia."

John Ross, director of forest protection with the Department of Natural Resources, says the issue is on the province's radar though it is in the hands of CFIA. Hemlocks are found throughout private woodlots, crown land, and provincial parks. He says the province is helping where they can, particularly with the surveys and sampling.

Both Ross and Neville say Nova Scotians should avoid moving firewood from one place to another and to buy firewood where you plan to burn it. HWA can spread by wind, animals, or human movement.

Neville says locals are encouraged to alert CFIA if they see any instances of HWA by calling 1-800-442-2342 or going to their website - www.inspection.gc.ca/pests

Statement from Parks Canada

Because of the close proximity to Kejimkujik National Park, Parks Canada is involved.

When contacted by LighthouseNOW, Parks Canada issued the following statement: "Parks Canada is working closely with the working group that is being led by the Canadian Food Inspection Agency. We are developing a protection and mitigation plan based on the most current information.

"Hemlock trees are an integral part of the forest ecosystems at Kejimkujik National Park and National Historic Site, so the recent discovery of this invasive pest near our park is concerning. Parks Canada is a recognized leader in conservation and we'll take every reasonable measure to protect the ecological integrity of the park."

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