Spruce bark beetle problem lingers

Peninsula's peskiest pest

Posted: Friday, June 16, 2000

Spruce bark beetles may be running out of trees, but peninsula residents are not out of the proverbial woods yet.

The spruce bark beetle epidemic is slowing from its peak year of 1996, but Kenai Peninsula forests still face grave threats, according to Ed Holsten, a scientist with the U.S. Forest Service who has been studying the epidemic since it began.

"There are still lots of beetles floating around," he warned.

Wednesday, Holsten surveyed the dwindling spruce grove around the Johnson Lake campground in Kasilof.

Five years ago, the state recreation area was densely forested. Now, campsites sit exposed in a field of stumps and dead trees.

"It's a goner," he said, pointing to a mid-sized tree.

Although its top was green and bursting with cones, telltale boring dust (woody debris that looks like rusty pencil shavings) lay about the base of the trunk. With an ax, Holsten peeled back a slab of scaly bark. Underneath, a pair of the tiny black insects were hollowing out a gallery to lay their eggs.

"With all the talk of the spruce beetle, you expect something the size of a German shepherd," he said. "It still amazes me that something that small can kill a spruce tree."

When the beetles land on a tree, they put out scent markers that attract others. By sheer numbers, the insects can overwhelm the tree's defenses.

The larvae hatch and devour the tree's phloem, the thin layer that moves nutrients from the needles to the rest of the plant. The trees starve, he explained.

Next summer, the infected tree will be red with dead needles. Two years after their parents arrived, the young beetles will emerge on a warm spring day to repeat the cycle. If the tree is warm enough, the cycle may take one year, he said.

Holsten pointed out another tree.

Blobs of resin, like moldy bubble gum, stuck to its trunk.

"This is what we call a 'pitch out,'" he said.

When beetles bite into a tree, the plant fights back by exuding sap. The spruce pitch pushes the insects out physically and contains natural insecticides, he said.

But water limits what trees can do. If a tree cannot take up water, it cannot bleed resin. Alaska beetles tend to fly early in the spring, while the ground is still frozen and trees cannot suck up moisture. They also thrive in warm, dry weather when plants are stressed.

"We have had a very good spring -- for beetles," Holsten said.

The beetles emerge when the weather warms and fly out to seek new trees to feed the next generation. Last year, the beetles near Kasilof flew June 17, but this year flights were reported before Memorial Day, he said.

Beetles linger nearly everywhere on the peninsula, and densities remain high near Anchor Point, from Moose Pass to Snow River and in pockets near Lake Tustumena. Biologists also worry about the forest on the south side of Kachemak Bay between China Poot Bay and Seldovia, he said.

Biologists have noted another threat to spruce trees.

Another insect, called the ips or engraver beetle, has been attacking trees along with the spruce bark beetles. It seems to be killing small and single trees logging operations have left behind to try to reseed cleared areas, he said.

Research entomologists such as Holsten are trying to find ways to trick beetles into leaving trees alone. They are studying natural insect scent markers that could repel or trap pests, he said.

When he works with some compounds, beetles find him irresistible and swarm onto his clothing, he noted.

The entomologists identified one marker that sends bark beetles the message, "This tree is taken, go somewhere else." It protects Douglas fir trees in other states, but scientists have yet to make it work on Alaska spruce trees, Holsten said.

"They are very tricky to use," he said. "The idea is to get the right blend and dosage."

Holsten and his colleagues are trying out compounds in traps near Cooper Landing, but they are far from having a foolproof spruce bark beetle repellent, he said.

In the meantime, homeowners can thin, trim and water trees to reduce their vulnerability. Professional advice is available for free. But during massive infestations, there is little one can do.

"It's like spitting in the wind," Holsten said. "You have very few options other than hold your breath and hope they miss your trees, or spray with insecticide."

Pesticides are controversial, but can be effective, he said.

Holsten recommended that people weigh the health threats against the dangers of wielding chain saws in the woods, and the environmental threats against the impacts of logging to clean out dead stands.

"It's an individual call," he said. "It's an emotional issue."

People will be dealing with the fallout from the infestation for years to come, he predicted.

Fire danger from the buildup of deadwood is a real and serious danger.

"I've seen it happen," he said. "These trees are incredibly flammable."

Another safety problem he cited is other trees that spruce had sheltered from wind, such as birch and cottonwoods.

"Now you have campgrounds full of decadent hardwoods prone to blow down," he said.

The cascade of ecosystem changes the beetle epidemic will produce is unpredictable, he said.

One major concern is the difficulty in getting new spruce to grow in cleared areas. The Sitka spruce of the south peninsula are easier to start than the white and Lutz hybrid spruce of the central peninsula. Moose prevent hardwoods from growing up in their place, he said.

"A lot of these stands will not regenerate," he said. "We are going to have a lot more open grasslands."

As consolation, Holsten predicted that the spruce bark beetle epidemic will be a once-in--lifetime event. History shows that other beetle outbreaks have occurred, but not like this.

"The outbreaks now are more intensive. They are different from what they were in the past," he said.

Holsten pointed to the warming trend of Alaska's climate over the past 100 years and the accumulation of mature, vulnerable trees as causes.

"I doubt that we'll see another outbreak like this for a long time. Maybe ever," he said. "If we do, it won't be for hundreds of years."

He predicted that the beetles will continue to cause trouble in pockets for years to come, but eventually will starve out and die back to their original role -- preying on a few wind fallen trees in the forest.

"The beetles won't disappear," he said.

Subscribe to Peninsula Clarion

Trending this week:


© 2018. All Rights Reserved. | Contact Us