2020-08-05

Government warns of invasive insect in local woods

by Keith Corcoran

  • <p>SOURCE: CANADIAN FOOD INSPECTION AGENCY</p><p>The hemlock woolly adelgid.</p>

Nature-lovers: Keep an eye out for a tiny cottonball-like pest creating big problems for a specific type of softwood tree.

The presence of hemlock woolly adelgid (HWA) in Queens and Lunenburg counties isn't threatening to human health, but is very destructive to hemlock trees, said Canada's food, animal, and plant watchdog.

"We haven't determined the extent of the spread as of yet," Ron Neville, a Canadian Food Inspection Agency (CFIA) plant health survey biologist, recently told LighthouseNOW.

"We are in the process of completing surveys over the next couple of months to determine what other sites there may be."

The invasive species is in the northwestern end of Lunenburg County, north of New Germany. It's also in "a number of spots" in Queens County, north along Highway 8 between Milton and the Annapolis County line, Neville said.

Moving untreated firewood is considered the most common way for HWA to spread.

HWA "looks like little white cottony egg sacks right now," Neville said, "and inside that egg sack there is one adult and there are eggs or nymphs that are developing."

Those cottony egg sacks, about two millimetres in size, would be found attached to the underside of a branch of an affected tree, Neville said.

The pest "feeds on cells at base of the needles, and when you have thousands feeding on a tree and stressing the tree, the needles die and fall off, the twig dies, and eventually the tree dies," he added.

HWA arrived in Nova Scotia in 2017 from the eastern seaboard of the United States. Experts believe the pests came to Virginia in the 1950s via infested nursery stock from Japan, and ventured northward over time. Infestation on Eastern and Carolina hemlock in the eastern U.S. "have resulted in significant levels of tree death, even destroying whole forests," the CFIA said.

Meanwhile, damage to Western hemlock in British Columbia is described as minor, and short-lived populations in Ontario were identified and stopped.

"All sizes and ages of trees are susceptible to attack by [HWA] ... and its presence threatens the continued existence of these two tree species in many locations," said the agency.

It's a slow death for the hemlock once HWA is introduced, Neville said.

"When you have a few on a tree, the tree can survive and sustain the infestation, but they reproduce quickly," he noted. "When the tree becomes more heavily invested, that's when the damage to the tree really starts to begin."

"It's not something that kills a tree in one year; it takes 10 or more years to kill a tree. Once it's present, it's very difficult to get rid of it."

If you see HWA, snap a picture, and send to the CFIA via https://www.inspection.gc.ca/pests on the internet.

"Hemlock is an important species ecologically within Canada," Neville said. "As more and more trees become infested, it can impact other species that rely on hemlock to survive."

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