Beetle invasion looms

Forester says that once an outbreak becomes an epidemic, there’s not much that can be done

Spruce beetles live and feed underneath the bark of the tree in the phloem layer, vascular tissue that transmits nutrients, said Kent Grant, district forester in Durango for the Colorado State Forest Service. Enlarge photo

STEVE LEWIS/Durango Herald

Spruce beetles live and feed underneath the bark of the tree in the phloem layer, vascular tissue that transmits nutrients, said Kent Grant, district forester in Durango for the Colorado State Forest Service.

WOLF CREEK PASS – Kent Grant pointed to a steep hillside where grayish swaths of timber marked stands of beetle-killed Engelmann spruce.

“This is what other areas could look like soon,” said Grant, the district forester in Durango for the Colorado State Forest Service. “The beetle kills started a few years back in the Weminuche (Wilderness) high country and spread rapidly.

“If you see a green tree among the beetle kill, it might not be a spruce, or it could be a spruce that hasn’t been attacked or hasn’t succumbed,” he said.

Grant whacked a dead spruce with his hatchet and peeled off a slab of bark.

“There could be some beetles here that didn’t get the word that the others were leaving,” Grant said, pointing to a larva and a callow adult whose snug quarters he had invaded.

Beetle hordes could be found soon near Silverton because it’s high country, too, Grant said.

In fact, the future is here, said Dave Crawford with the U.S. Forest Service’s Columbine District.

“We have some beetles in two patches of blown-down spruce,” Crawford said. One is 28 acres in size about a mile from Coal Bank Pass, and the other is 280 acres just north of there.

“It’s not a lot of acreage, but it’s kind of significant because it’s way on this side of the Weminuche,” Crawford said.

Blowdowns make an instant breeding ground for beetles, Crawford said, because a downed tree no longer has natural defenses.

Spruce beetles have devastated 250,000 acres in the Rio Grande and San Juan national forests, Crawford said.

The beetle threat is serious enough to bring Sky Stephens, a Colorado State Forest Service entomologist, to Durango and Pagosa Springs next week for two lectures.

Stephens, whose visit is sponsored by FireWise of Southwest Colorado, will discuss challenges to forest health, including beetles, other insects and disease.

“We’ve done a program every year since 2003 in anticipation of Wildfire Prevention and Education Month, which is May,” FireWise director Pam Wilson said. “We want to motivate people to get their property in shape.”

Grant provided a crash course on the spruce beetle, which also has an appetite for blue spruce.

The spruce he cut into also exhibited exit holes of departing beetles and pitch tubes – excretions that trees exude to eject invading beetles.

Boring dust, often present at the base of the tree, was missing. Grant surmised melting snow had washed away the telltale evidence of the invasion.

The bark beetle that attacks Engelmann spruce is a purplish, pinhead-sized insect with a two-year life cycle.

Hundreds to thousands of beetles can be found in a single snag, Grant said.

The beetle bores through the bark and makes itself at home in the phloem layer, a living part of trees that carries nutrients.

“That’s the food cache,” Grant said. “That’s where the goodies are.”

In the second year, a new generation of beetles emerges to attack new trees, he said.

Small spruce often are spared because they don’t have enough nutrients, Grant said.

“Once an outbreak becomes an epidemic there’s not much you can do,” Grant said.

The spruce, which has a shallow root system, is vulnerable to high wind or avalanches, Grant said. Beetle infestations can easily occur in these blowdown areas.

The spruce is under stress from the drought, making it an easy target for beetles, Grant said.

The loss of spruce ripples through the environment:

Less shade means that snow melts earlier and faster.

Dead standing trees are a danger to automobiles and hikers. In the 2002 Missionary Ridge Fire, a tree fell without warning and killed a firefighter.

Forest management through thinning and logging helps keep trees healthy, but it has to be done before beetles gain a foothold, Grant said.

Downed trees accumulate to provide ready fuel for wildfires.

Wildlife may be affected. Raptors choose snags as nesting sites, but there will be no coneys, no squirrels or other seed eaters.

Private landowners who have prized spruce near their houses may elect to spray them rather than fell them, Grant said.

“It has to be done before they become infested,” Grant said. “Afterward is too late.”

Dead spruce make good house logs if they’re harvested soon enough, Grant said.

Engelmann spruce take a long time to regenerate because they like shade, Grant said. Without shade, they have to wait for ponderosa pine or fir to move in and create a canopy so a stray spruce seed can restart the process.

“It takes 35 to 75 years for a spruce to reach 4½ feet in height, what we call ‘chest tall’ because that’s where we measure a tree,” Grant said. “It will be centuries before we see forests like this again.”

daler@durangoherald.com

Kent Grant, district forester in Durango for the Colorado State Forest Service, said the spruce beetle infestation started a couple of years ago in the Weminuche Wilderness high country. Enlarge photo

STEVE LEWIS/Durango Herald

Kent Grant, district forester in Durango for the Colorado State Forest Service, said the spruce beetle infestation started a couple of years ago in the Weminuche Wilderness high country.

Kent Grant, district forester in Durango for the Colorado State Forest Service, holds a slab of bark from an Engelmann spruce harboring the larvae of a spruce beetle recently on Wolf Creek Pass. Enlarge photo

STEVE LEWIS/Durango Herald

Kent Grant, district forester in Durango for the Colorado State Forest Service, holds a slab of bark from an Engelmann spruce harboring the larvae of a spruce beetle recently on Wolf Creek Pass.

Beetle-killed Engelmann spruce contrast sharply with live vegetation in Porphyry Gulch in the Weminuche Wilderness. Beetles have ravaged 250,000 acres of spruce in the San Juan and Rio Grande national forests in Southwest Colorado. Enlarge photo

Courtesy of Anthony Garcia/U.S. Forest Service

Beetle-killed Engelmann spruce contrast sharply with live vegetation in Porphyry Gulch in the Weminuche Wilderness. Beetles have ravaged 250,000 acres of spruce in the San Juan and Rio Grande national forests in Southwest Colorado.

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