Scientists track invasive species discovered in Haldimand woodlot

A pilot community-science project that uses a 3D-printed trap is helping scientists track an invasive species discovered in a Haldimand County woodlot.

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The hemlock woolly adelgid (HWA) is a tiny insect that’s difficult to spot, however its presence can be determined by the wool it creates to protect itself and its eggs.

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“We compare it to the tip of a cotton swab,” said Victoria Derry, a forest health biologist with Natural Resources Canada. “Through the spring in particular, they make these very fluffy, woolly masses that will be found on the underside of a branch at the base of the needles.”

HWA are thought to have come from Japan and were first discovered in the Richmond, Virginia area decades ago before spreading throughout much of the eastern United States.

“In Canada the bug was discovered in southern Nova Scotia in 2017 causing significant mortality to old-growth hemlock forests,” said Laura Thomas of NRC Science Communications. “A large infestation was found in the Niagara region in 2019 and since then there have been one or two new detections every year in Ontario.”

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HWA spread through bird migration at the crawler stage when they stick to birds’ legs and feathers.

In recent years several communities had to cut down many ash trees to combat an infestation by the emerald ash borer.

Derry said HWA infestations can be devastating in the same way because trees, once infested, are susceptible to death within three to 10 years. The insect kills the tree by sucking the sap at the base of needles and draining the tree of its energy.

Along with looking for the woolly masses, the biologist said people should watch for signs that a hemlock tree might be struggling. Indicators include the loss of foliage and branches, the tree not growing well, and a lack of bright green tips at the edges of the branches.

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Hemlock trees are conifers that look like a classic Christmas tree but shorter in height with shorter, flat needles that do not grow around the entire branch or twig.

Found near rivers in southern Ontario, hemlocks provide bank stabilization, and are an important deer habitat, according to biologists.

The 3D-printed traps are being deployed in woodlots containing hemlock trees, and Derry noted that while people who may have a hemlock on their property can register online, placement of the traps may end up in higher-risk areas.

“We are trying to basically double what we did last year with a major focus on Southwestern Ontario,” she explained, adding that Natural Resources Canada wants to determine where hemlocks are located.

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The Canadian Food Inspection Agency, in partnership with NRC has an app called Survey 123 that people can use to help identify specific insects.

“If (people) suspect that they have HWA they should contact the CFIA – the investigative and regulatory body that deals with it – that has trained inspectors they can deploy when there is a reported suspicious insect or disease.”

The 3D-printed traps are an orange-colored disc mounted on a stand with microscope slides dipped in petroleum jelly to trap the HWA at the crawler stage. Participants mail back the slides for inspection and DNA analysis and will receive new slides annually.

Thomas said early detection is crucial for halting the spread of the woolly pest, and people who own or manage property with hemlock trees in Southwestern Ontario can join the Hemlock Woolly Adelgid Monitoring Network at invasivespeciescentre.ca.

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