2021-06-16

Government asks public to be on lookout for cotttonball-like insect that feasts on hemlock

Provincial and federal agencies are going into another year of trying to manage and reduce the spread of a small-sized, invasive pest creating big issues in Lunenburg County's wildland and other forests in the western end of the province.

The tiny, cotttonball-like insect is the hemlock woolly adelgid (HWA), which damages and can kill the softwood tree of the same name. The insect takes the appearance of two-millimetre-sized white cottony egg sacks attached to the underside of a branch of an affected tree. The HWA feed on cells at the base of the needles. The stress causes the needles to die and fall off, then the twig dies, and so, eventually, does the tree.

Forestry officials pinpointed the HWA four years ago, and most recently last year on Crown land in Lunenburg County. It is believed HWA came here from the eastern seaboard of the United States. Experts maintain that the pests came to Virginia in the 1950s via infested nursery stock from Japan, and ventured northward over time.

While the pest does not pose a threat to human health, as well as its impact on hemlock - considered an important species ecologically within Canada - it could also affect other species that rely on hemlock to survive.

Dan Lavigne, who is in charge of forest protection risk services within Nova Scotia's Department of Lands and Forestry, said several measures to better understand the insect and look at various detection and management alternatives to help slow its spread are being carried out or are under consideration in 2021 and beyond.

Silviculture thinning in stands where HWA is located is one.

"By opening the stand, you actually increase the rigour of the remaining trees that are there because they have less competition from others and may help manage the insect," Lavigne told LighthouseNOW during a recent phone interview.

Other considerations are chemical treatments that provide up to seven years of protection for trees, along with finding and possibly introducing potential predators or parasites that may target HWA.

Yet another measure might be collecting seed from hemlocks and preserving it so lost sites can be rehabilitated.

"There are going to be some areas where you won't be able to protect all the trees and what will happen is you're going to have different species come in and those sites will change over time," Lavigne said.

For new invasive species like HWA, Lands and Forestry works with its partners, such as the Canadian Food Inspection Agency - Canada's food, animal, and plant watchdog - in various forest pest related issues.

"Trees can die from this tiny, tiny little insect that you can hardly see with the naked eye," Lavigne said of the HWA.

There is nothing climate-related that appears to limit its spread. Moving untreated firewood is considered the most common way for HWA to move to different areas.

Lavigne encourages the public to educate themselves about the insect, follow government regulations pertaining to transport of hemlock wood products and report potential HWA sightings to provincial or federal authorities.