Spruce trees suffer infestation in Alaska

ALLEN MARQUETTE

April 25, 2008 at 10:53AM AKST

For The Cordova Times

What is black, a quarter-inch long and responsible for more than 2.3 million acres of cumulative tree destruction in Alaska since 1992?

If you guessed the spruce bark beetle as the culprit, you’d be correct.

The area affected is the largest area of tree mortality from a single insect outbreak documented to date in North America. Unfortunately, the future does not look promising for spruce trees in Alaska or other Western states.

One reason for the increased spruce tree damage is global warming.

Since winters are gradually becoming milder throughout Alaska and other areas of the Pacific Northwest, pine beetles are not only surviving but also thriving.

In previous decades, colder winters helped keep the beetles in check by killing off large numbers of their species each winter, slowing their spread and survival rate.

At the same time that spruce bark beetle activity has increased in Alaska’s boreal forests of Interior Alaska, so has other forest insect activity. Spruce budworm, coneworm and larch sawflies are also contributing to attacks on our forests in Alaska.

Changes in spruce bark beetle activity are most easily illustrated by looking at the Kenai Peninsula spruce bark beetle outbreak; in just eight years from 1989 to 1997, the beetle damage expanded from approximately 40,000 acres to more than 1 million acres.

Besides loss of natural habitat for plants, animals and birds, living trees also provide many jobs and dollars for communities throughout Alaska that harvest timber. When spruce bark beetles and other insects kill off large areas of the forest, the potential for devastating forest fires also becomes much higher.

Erosion and soil degradation is a concern too as dead trees loose their ability to hold the soil and rocks in place, which can lead to silting of streams and rivers severely impacting fish and their spawning activities.

Beetles live in the thin phloem or growing layer between the bark and the wood, which does not damage the wood inside the tree. Although the wood remains undamaged by the beetles and can be harvested, the deforestation of large areas of forest has greater consequences.

Beetles produce chemicals called pheromones to communicate with other beetles – for mating, to locate susceptible host trees and to repel other spruce beetles.

So, you may ask what can you do to help prevent the spread of spruce bark beetles? Cutting and collecting firewood in Alaska is a widespread activity and on the increase with the high cost of heating oil. If you collect firewood, check the wood before you bring it home.

If you notice insect damage just under the bark and live beetles and or eggs inside the tree, realize that by transporting the wood to your house you might be providing bark beetles a way to new unaffected areas as well as exposing trees around your house to insect infestation.

On a brighter note, spruce trees also produce chemicals that can affect beetle behavior. These chemicals show potential for modifying beetle behavior and reducing the severity or even preventing damaging infestations.

As scientists develop more strategies and better ways of slowing down or preventing insect infestations, perhaps Alaska’s spruce forests will thrive once again.

> Allen Marquette is the education programs coordinator for the Prince William Sound Science Center.