Spruce beetle outbreak spreads as experts advise tackling the problem now

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Anchorage (KTUU) — An outbreak of spruce beetle seen across parts of Southcentral Alaska since 2016 was mentioned in Thursday’s gubernatorial debate as an example of the impacts of climate change. Experts are recommending that homeowners check their trees now as beetles will fly again in May.

Aerial surveys conducted this summer by state and federal agencies found almost 558,000 acres of spruce beetle damage across Southcentral Alaska, with the overwhelming majority of the damage concentrated in the Matanuska-Susitna Valley.

Since 2017, there was a 46 percent rise in spruce beetle-caused tree mortality across Alaska.

“When you think of the impacts, we’re ground zero when it comes to climate change,” said Democratic gubernatorial candidate Mark Begich in Thursday’s debate. “When you see acidification in the waters and warming the waters and impacting our fisheries, when you look at what’s happening to the spruce bark beetle and the impacts of our forestry, all of this and many more things are impacting, we can do our part.”

Elizabeth Graham, an entomologist with the U.S. Forest Service, said that climate variables do have a direct link with the ongoing spruce beetle outbreak but she highlighted there are other factors at play.

The beetle, which is native to Alaska, is systemic to the forest, Graham says, and plays an important part of helping trees decompose. Under the right conditions though, the beetle can spread quickly and cause widespread damage.

Graham said the Mat-Su Valley has been “hit really hard and really fast” by the outbreak, caused in part by drier summers and milder winters, prime forest conditions and a changed life cycle for the beetle.

Drier summers mean spruce trees have less capacity to create sap, their best defense against attacks by the beetle, said Graham. Milder summers can even change the ways beetle grow from egg, to larvae, to being able to reproduce.

“It used to be we would mostly see a two-year life cycle, but with a milder summer they’re able to feed and be more active longer and switch to a one-year life cycle,” said Graham. “That’s like double the amount of reproductive capacity.”

Milder winters also result in less beetle die-off, giving the trees less respite from attack.

In the mid-1990s, the Kenai Peninsula was struck by a similar spruce beetle outbreak which dwarfs the one currently seen in the Mat-Su Valley.

Graham describes that outbreak as starting for similar reasons: Prime weather conditions were exacerbated by almost pure stands of slow-growing large white spruce, proving to be prime targets for the beetle.

John See, a forester with the Anchorage Fire Department, said Anchorage had recently seen a unique way for the beetles to spread; a spring windstorm caused spruce trees to fall over, weakening them from defending themselves.

He said anecdotally that arborists tell him about regularly encountering beetle-killed trees in the Anchorage bowl. Some arborists told Channel 2 they had seen impacted spruce around Turnagain Arm and even around Hillside.

Graham encourages calm though, saying the epicenter of the outbreak was still in the Mat-Su Valley. The data presented by state and federal agencies showed that the entire Anchorage-area had 1,500 acres of impacted trees in the past year.

Mitigation efforts
For homeowners, John See described that his department offers a cost-sharing agreement for tree removal. Starting in spring, AFD is set to receive another grant that allows them to offer up to $500 per household for tree removal when a firewise assessment takes place.

When it comes to spruce-beetle mitigation, Jessie Moan, who works in pest management with the University of Alaska Fairbanks Cooperative Extension Service, said once a tree has been attacked by the beetle, there is nothing that can be done to cure it.

The focus becomes removing damaged and dying trees and protecting high-value healthy trees.

See has had personal experience with that last process, explaining that as the representative of his homeowners association, he organized a pesticide spraying effort, which around 20 of 60 homeowners took part in.

He described the average cost as around $175-$200 for the first three trees with $25 per additional tree. The spraying process would protect the trees for three years, said See.

Graham said for people who don't want to use pesticides, that they can keep "their trees happy" by keeping them watered, increasing their defenses against the beetle.

As winter approaches, Moan had a list of recommendations:

1. Check trees now in order to know the status of your trees and have plenty of time to make plans for any management that may need to occur over the winter or in the spring.
2. Activities that can be completed in winter months include tree removal activities and pruning activities. Tree removals are the activity (not spraying) that shouldn't be done between May and July because that can exacerbate spruce beetle problems.
3. Sprays should be done in late April or early May (dependent on weather conditions). Ideally, sprays are applied before the beetles are active in order to ensure adequate tree protection. Sprays that occur during the active adult flight period (mid May-July) will not make a spruce beetle situation worse, but it may be difficult to ensure that the trees being treated are not already attacked.

In terms of forest-wide mitigation, there is not much that can be done according to Graham. Spraying pesticides on a forest-wide scale is not considered practical. Instead, the focus is on removing dead and dying trees and spacing out the remaining spruce.

Graham described a “boom and bust” cycle to spruce beetle populations — when there was not enough spruce to eat in the Mat-Su Valley, their population would likely crash back down to what it is in normal years.

State and federal agencies have joined together to launch a new website offering information about spruce beetles, tips for identification and how they are managed.