By JIM MANN

The Daily Inter Lake

You have to look closely at the sun-baked slopes of the Swan Mountain Range, and the infestations become clear.

Blended into the green tapestry of mixed forest canopies, there are blotches of "red and dead."

Douglas fir beetles and other invading insects that did the damage already have moved on, and next summer there will be new patches of dead trees.

The outbreak has spread rapidly during the past 10 years, with beetle swarms exploiting trees stressed by drought, overgrowth due to fire suppression, parasitic mistletoe, root rot, and other disease.

Every year, the U.S. Forest Service conducts aerial surveys to size up the progressive damage.

"You are always going to see some insects and disease at background levels in the forest," said Amy Gannon, entomologist with the Montana Department of Natural Resources and Conservation. "It's when it gets to outbreak levels that you need to manage for."

On the Swan River State Forest and surrounding lands, the Douglas fir beetle and fir engraver infestations have reached outbreak levels in recent years.

Last year's aerial survey map shows hundreds of brown polygons designating bug and disease kills over the Mission and Swan mountain ranges.

On the Swan River State Forest alone there were 2,400 acres of new infestations in 2006.

On all forest lands in Flathead County, 64,926 acres were impacted by insects and disease last year, with mountain pine beetle accounting for a third of the damage. In Lake County, 35,719 acres were impacted by insects and disease.

Gannon said forest lands across the state have been affected to varying degrees, with some of the largest outbreaks occurring in the Bitterroot Valley. The most prevalent insect statewide is the mountain pine beetle.

But in the Swan Valley, it's the Douglas fir beetle.

"I'm surprised to see how much Douglas fir beetle activity they have there," Gannon said.

A beetle-killed stand of Douglas firs in the upper reaches of the Cilly Creek drainage reveals telltale signs of what has occurred.

Kristen Baker, forest management supervisor on the Swan Forest, points out "pitch streamers" dribbling down the bark of a huge Douglas fir killed by beetles last year.

She explains how thousands if not millions of the tiny insects swarmed the tree for at least 50 feet up the trunk. The tree responded by secreting sap in an effort to "pitch" out the invaders.

The beetles bored out maze-like "galleries" under the bark. They laid eggs and overwintered in the tree, emerging and flying on to new targets in late May or early June.

"That tree is still green," Roberson said. "But as summer progresses it will turn red."

Roberson points out white fans of fungus at the base of many other trees in the area - Armillaria root disease that weakened them and made them more vulnerable to beetles. Some trees also were compromised by tangles of dwarf mistletoe.

All of the bug-killed trees have been stressed by years of drought conditions.

"The beetles can sense when trees are under stress and when their attacks will be successful," Roberson said. "There's a lot of things working together in their favor."

The decaying stand is situated in the heart of the recently approved Three Creeks forest management project area, where the Douglas fir beetle caused heavy Douglas fir mortality on 2,500 acres between 2000 and 2004. Tree mortality has advanced significantly within the project area since then, Roberson said.

Similar damage has occurred throughout the 40,000-acre Swan River State Forest. And that presents a problem for the Department of Natural Resources and Conservation.

While some view insects and disease as part of a natural process with no need to salvage dead and dying trees, that's not an option for the state agency, which is constitutionally mandated to generate revenue from state forests for school trust funds.

"Some folks would have those stands die and burn," Roberson said. "That doesn't help us meet our mandate for the school trust. We are not a preserve."

Salvaging dead and dying timber is a priority for the Three Creeks project, along with meeting a state timber target that requires an annual harvest of 6.7 million board feet from the Swan Forest.

The forest grows an estimated 7 million to 12 million board feet of timber annually, but decaying stands are considered "negative growth," contrary to the state's sustained yield standards.

Roberson shows off a healthy old-growth stand, dominated by larch, covering nearly 500 acres in the lower Cilly Creek drainage.

"It's growing wood instead of decaying and dying," he said. And for that reason, the stand is not a target for logging in the near future. "It's a high-value asset for the trust in the future."

The Three Creeks project is expected to generate 20 million to 26 million board feet of lumber over the next three years.

Forest managers are planning another multiyear project, called White Porcupine, that will largely focus on stands with different insect and disease problems on the western fringes of the forest starting in 2009. The fir engraver has infested grand fir stands in that project area, where there also is a heavy presence of white pine blister rust and Indian Paint Fungus.

The fungus basically eats its way upward through tree stems, emerging on the bark in the form of mushroom-like "conks" that absorb water.

As Roberson describes it, the tree becomes a "culvert" for water. On cold winter days, the moisture-laden trees pop vertical frost cracks that can eliminate any commercial salvage value.

"On this side of the forest, we have thousands of acres of this stuff," Roberson said, referring to stands with the varying insect, disease and fungus damage.

The Three Creeks and White Porcupine projects also are aimed at converting tree species in areas where logging occurs. Instead of regenerating Douglas fir that will be susceptible to the same insects and disease, there will be efforts to establish more-resistant Ponderosa pine and western larch stands.

Gannon will lead a forest insect and disease field day in the Flathead on Aug. 3.

The bus tour, sponsored by the DNRC, is open to the public and will be geared largely for private timberland owners. Those interested in participating should contact Gannon at her Missoula office, 542-4283.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com