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Scientist: Spruce bark beetle epidemic slowing but still active

Posted: Friday, June 16, 2000

KENAI (AP) -- Spruce bark beetles may be running out of trees on the Kenai Peninsula, but residents aren't out of the figurative woods yet.

The beetle epidemic is slowing from its peak year of 1996 but Kenai Peninsula forests still face some serious threats, said 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 said.

Holsten spent much of Wednesday surveying the dwindling spruce grove around the Johnson Lake campground at 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, boring dust (woody debris that looks like rusty pencil shavings) lay about the base of the trunk. Holsten used an ax to peel 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. The insects can overwhelm the tree's defenses by sheer numbers.

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, Holsten said.

The infected tree will be red with dead needles next summer.

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, then the cycle may take one year, he said.

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

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 told the Peninsula Clarion. ''The idea is to get the right blend and dosage.''

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

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

Fire starting in the buildup of deadwood is a real and serious threat.

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

Another safety problem comes from other trees that the spruce had sheltered from the wind, such as birch and cottonwoods.

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

Beetles will continue to cause trouble in pockets for years, but eventually will starve and die back to their original role -- preying on a few windfall trees, he said.

''The beetles won't disappear,'' Holsten said.



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