Tongass Budworm Outbreak Ebbs

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Category: State News

Created on Friday, 28 July 2023 15:24

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By Marc Lutz

Wrangell Sentinel editor

Scientists and staff with the U.S. Forest Service are hopeful that the blackheaded budworm outbreak that began three years ago throughout the Tongass National Forest is beginning to decline.

Data collected earlier this year revealed not only the extent of the damage done by the half-inch insect but evidence showed the worms are dying off.

Elizabeth Graham, an entomologist with the Forest Service, said in a news conference on July 20 she has seen firsthand that there is lower activity of the bug on Douglas Island near Juneau, and that many are “sickly.”

Since Juneau and Haines were on the northern fringe of the outbreak, she suspects other areas, including Wrangell, are further along in the recovery process.

Outbreaks typically last about three years. The last time the Tongass endured a budworm outbreak was from 1992 to 1995. Budworms usually succumb to viruses and parasitic wasps, reducing their numbers.

Diagnosing a virus-stricken worm is sometimes a challenge, Graham said, but “when they get that virus, they get real gooptified.”

Earlier this year, Forest Service staff conducted aerial mapping of the 17-million-acre Tongass, noting areas of deforestation. Then, on-the-ground data collection in certain areas would show whether the damage caused by the worms was top kill or total destruction of the trees.

Austin O’Brien, the timber staff officer in Wrangell, said he hesitates to call the declining numbers of

blackheaded budworm a recovery, but the outbreak has diminished.

He believes the outbreak this time around was only made worse by prior damage done by sawfly to the hemlock trees the worms tend to feast on. “One or the other by themselves is not nearly as impactful,” O’Brien said.

Combined, it’s easy to see the affected trees. Sawflies are another defoliating insect in their larval or worm stage.

The results of the damage can be seen from many vantage points throughout Wrangell, appearing as long grayish-brown swathes of trees surrounded by greener growth.

“The hemlock sawfly targets second- and third-year needles of a tree, whereas the blackheaded budworm focuses on this year’s growth,” O’Brien said. “When you get the two of them together, it basically defoliates the entire tree.”

Although the outbreaks aren’t necessarily good for the timber industry, they can be beneficial from an ecological standpoint, said Molly Simonson, a silviculturist with the Forest Service.

“One of the benefits to a standing tree dying is that it can take a long time for it to fall to the ground,” she said.

“One of our concerns would be if there is a lot of large woody debris (fallen) down that could impede deer movement.”

Trees that die and eventually rot and fall to the forest floor would also open up the canopy, allowing other flora to grow and thrive. It could create an avenue for more red and yellow cedar trees to spring up.

“There’s a chance for other species to take hold if it’s been hemlock-dominant,” Simonson said. “Old-growth forest continues to change over time, especially because of these mortality events.”

Another challenge faced by Forest Service staff is determining which trees are affected by the worms or disease and those that are eaten by another ravenous creature, the porcupine.

O’Brien said it’s not uncommon to see a tree that looks as though it has been destroyed by the worms. Upon closer inspection, the bark has been stripped away. A prickle of porcupines will tackle a hemlock like a buffet, eating its outer defenses and leaving it to die before moving on to the next meal.

But as for the trees impacted by the budworms, expect healing to occur, Simonson said.

“The forest is entering recovery mode right now,” she said. “The trees will look bad for a few years but are slowly starting to grow new needles. We expect most trees to recover from the outbreak.”