Nova Scotia

Hemlock tree-destroying pest arrives in Nova Scotia

A hemlock tree-destroying pest has turned up in Nova Scotia and count on frosty temperatures to kill these tiny adaptable critters.

Hemlock woolly adelgid has been found in 5 Nova Scotia counties

The hemlock woolly adelgid appears as white, woolly sacks on the base of needles of the hemlock tree. (CFIA)

A hemlock tree-destroying pest has turned up in Nova Scotia and don't count on frosty temperatures to kill the tiny beasts. 

The hemlock woolly adelgid attacks eastern hemlock trees by feeding on the nutrient and water storage cells at the base of the trees' needles, killing them. 

Ron Neville, a plant health survey biologist with the Canadian Food Inspection Agency, is investigating how far the pests have spread throughout the province since they were first detected here in mid-July.

So far, the hemlock woolly adelgid — or HWA — has been found in five counties: Digby, Yarmouth and Shelburne and a few sites in Annapolis and Queens.

"In Digby and Yarmouth County, it's fairly widespread and less so in Annapolis and Queens," Neville told CBC's Information Morning

'It looks like a small cotton ball'

The eastern hemlock grows from Ontario east to the Maritimes, often on the shores of lakes and rivers.

"Loss of hemlock trees can have a potential, major ecological impact. Hemlock in many forests serves as a foundation tree in the environment so what that means is that other species that live in those areas depend on hemlock for their existence," said Neville. 

The tiny insect, less than 1.5 millimetres long, produces a wool-like wax to protect its eggs, which are usually deposited on the underside of hemlock needles at the tips of the branches.

The hemlock woolly adelgid can spread on the wind or by birds or animals. They often hitch rides on nursery stock and wood products like firewood. (CFIA)

"It's very tiny, it looks like a small cotton ball. And those develop over the winter and they're most obvious, basically, from January through to June," said Neville. 

The pests are native to Asia and Neville said it's believed they first arrived in North America in the 1950s in the state of Virginia, spreading across the northeastern U.S.

Able to adapt to cold climates

The CFIA already has rules demanding that hemlock seedlings or wood products being imported to Canada must have a certificate showing they are free of the pest. The insects often hitch a ride on nursery stock and wood products like firewood.

They can also be transported by birds, animals and even on the wind. 

The hemlock pest also very adaptable, able to survive cold winters as well as warm ones, according to Natural Resources Canada. 

In terms of what to do about the pests, Neville said the CFIA is looking at what our neighbours to the south have done. 

One option is to just remove affected trees but that could have a devastating effect on forests. 

As its name implies, the aphid-like hemlock woolly adelgid attacks eastern hemlock trees. (CFIA)

In parts of the U.S., forestry officials have attempted to control the spread using biological controls including importing lady beetles from Asia to eat HWAs. However, Neville cautions that introducing a new species into an ecosystem can bring about a whole new set of problems.

"We have to consider the implications of bringing in a predator pest," he said.

If you think you have an HWA infestation, check with the Canadian Food Inspection Agency or call 1-800-442-2342.

With files from Information Morning