Beetle Epidemic Increases Fire Hazard

June 12, 2003
Shaun McKinnon, The Arizona Republic

Scientists are calling Arizona's bark beetle infestation one of the worst in U.S. history even as fresh armies of the ravenous bugs spread through the state's drought-weakened forests.

Last year, the tiny insects killed more trees in Arizona than all of the wildfires and threaten to scar more than 1 million acres of forest, an area the size of Rhode Island, by the end of this year. Virtually nothing can stop the beetles until the drought breaks, and even then, millions of dead trees will remain on a landscape forever altered.

"This is certainly the largest engraver beetle epidemic I have ever seen and probably that anybody's ever seen," said David Wood, a University of California-Berkeley entomologist who has studied bark beetle infestations throughout the West. "They are really more akin to fire, when you see such massive mortality over a two-year period."

Wood surveyed forests near Prescott this spring to help Arizona Public Service Co. figure out how to safeguard about 2,100 miles of power transmission lines that run through potentially infested areas. Similar surveys by the U.S. Forest Service and the University of Arizona will help authorities try to calculate the enormity of the damage.

So far, officials estimate about 800,000 acres of private, state, tribal and federal land have been infested, killing more than 6 million trees. Those numbers have swollen from fewer than 50,000 infested acres in 2001, and are expected to grow significantly as the next generations of beetles swarm this month.

Survived winter well

How much is unclear, according to forest health scientists. The beetles that hibernated last winter fared well, said Tom DeGomez, state forest health specialist for the UA. The offspring of those adults have shown up in stands of piñon pines, while the offspring of a separate species will begin to emerge in ponderosa pine forests in the coming weeks.

"This first generation of 2003 is going to be pretty aggressive," DeGomez said. "That's what the pattern has always shown. We expect the June flight to be pretty virile."

Outbreaks elsewhere

Similar outbreaks are reported in New Mexico, Colorado and Southern California, where trees are dead or dying across more than 200,000 acres in the San Bernardino and Cleveland national forests.

Hardest hit in Arizona are forests near Prescott, Crown King, Horsethief Basin, Pine and Strawberry, as well as wide bands of trees near Flagstaff and Winslow. In some areas, tree mortality is nearing 90 percent.

John Anhold, a U.S. Forest Service entomologist and forest health chief for the region, said a more accurate picture of the devastation will come later in the summer, when flyovers of the forests resume. Already, signs of newly infested trees are evident around Flagstaff, indicating an early start to the attacks.

Fire danger threat

The most immediate threat is fire danger. As the already dry trees die, they turn into upright kindling. Gov. Janet Napolitano has asked the federal government for as much as $232 million to help clear dead trees near towns, highways and utility corridors.

Downed power lines would create a serious fire risk, which is why APS commissioned Wood and a California consulting company to survey forests, said Mike Neal, the utility's forestry manager.

"We flew the area today and saw a lot of trees that four months ago were green and today are olive," Neal said. "That means they're infected. It's definitely spreading."

APS after trees

APS wants to remove any dead trees that could possibly fall onto a power line or pole. The utility is working on a plan with state and federal authorities as well as private landowners. Neal said beetle-infested trees will typically stand for two or three years before they begin to fall.

Bark beetles are no strangers to Arizona's forests, but the drought has allowed them to multiply in unprecedented numbers. Beetles burrow into trees and feed on the inner bark, destroying or clogging the tissues that move water from the roots to the branches. They also lay eggs inside the trees.

Years not normal

In normal years, the trees would produce enough resin to ward off beetle attacks, but drought has drained them of their defenses. Once the beetles have infested a tree, it's too late to do anything; the tree will die.

Insecticide can be effective in small areas but it won't work on a forestwide scale. The beetles will spread until they run out of trees or until the trees regain enough strength to thwart the attack.

Especially vulnerable

Scientists say Southwestern forests were especially vulnerable when this drought hit because they are so dense, leaving fewer resources and less water to go around as moisture levels plummeted. One way to avoid another infestation is to thin the forests, Wood said, an option that draws quick opposition from many environmental groups.

"If we don't kill the trees, the beetles will," Wood said. "It doesn't make any difference where you come down on the political spectrum, it will happen. If we don't manipulate density and species composition, the beetles will have their way as they're proving right now."

http://www.azcentral.com/arizonarepublic/news/articles/0612barkbeetle12.html