By John Tonin
Yukon forests remain healthy according to the 2020 Yukon Forest Health Report, however, there are areas that foresters will be monitoring, said Rob Legare.
The Yukon Forest Health Monitoring Strategy focuses on the 10 forest health agents of greatest concern. The Yukon is divided into five forest health zones.
Each year since 2009, researchers have completed aerial surveys of one of the five zones. But, because of COVID-19, Legare said the aerial study was unable to happen in 2020. Instead, the information provided was an “anecdotal judgement” of what has been known to be occurring.
In 2021 foresters will be back in the air doing aerial monitoring in Zone 3, or the Dawson region.
Aerial surveys will be done in Zone 3 because of spruce budworm. In 2019 and 2020, residents of Mayo reported light defoliation on the tops of spruce trees in the Stewart Crossing area on Ferry Hill.
“When you see it (spruce budworm) in one area, it is very likely that it is in another area,” said Legare.
High budworm populations can result in defoliation ranging from light damage to growing tips to complete tree defoliation, reads the report.
Legare said their forester counterparts in the Northwest Territories have also been reporting budworm on the Yukon side of the border.
“They see it in the Yukon, they are seeing it in the Peel,” said Legare. “We don’t normally fly the Peel Watershed but we are including the Peel so we can start mapping spruce budworm because Northwest Territories’ forest health personnel are seeing it there.”
In the Shallow Bay area, there is “quite a bit of windthrow” said Legare. Windthrow refers to trees uprooted by wind.
“When there is windthrow of conifers that becomes available hosts for bark beetles,” said Legare. “The beetle likes trees that are stressed.
“What the risk is the large amount of windthrow could attract the beetle and populations can build up. We are monitoring those areas right now and doing some removal of host materials.”
Legare said there will be more information on the windthrow situation in the 2021 Forest Health Report.
Perhaps the largest area of concern still remains the territory’s aspen populations.
“The real extent of disturbance in the North is the aspen decline,” said Legare. “People up there have been noticing that the aspen just haven’t looked that healthy.”
Legare said the aspen decline could be attributed to climate change because it’s something that’s occurred in the last 20 years. Climate change can lead to changes in pest distribution, severity and frequency which contributes to aspen decline.
There are two species affecting the aspen decline, the large aspen tortrix and the aspen serpentine leafminer.
Outbreaks of large aspen tortrix have occurred in several places throughout the Yukon including Teslin Lake, Braeburn, Haines Junction, Pelly and Champagne. The tortrix eats the aspen leaves.
The leafminer pest occurs throughout the Yukon range of trembling aspen and also defoliates balsam poplar. The leafminer causes the aspen leaves to turn a milky white.
Although there are some areas of concern, Legare said when the aerial surveys are conducted foresters usually just see rows upon rows of beautiful, healthy trees and rivers.