Beetles' Bite Bad For Ponderosa Bark


When Rim country resident Cathy Stevens looks out her kitchen window, she worries because the dark green forest behind her Alpine Heights home is dotted with dead and dying ponderosa pines.

Bark beetles, which thrived during the long, hot summer last year, killed a number of ponderosa pines in the Payson and Pine-Strawberry areas last fall, and with the onset of spring, the damage has suddenly become obvious.

Stevens, who teaches kindergarten at Payson Elementary School, said the dead trees are clearly visible from her deck and her kitchen window.

"There has been a really bad infestation where I live," she said. "It's horrible to look out the window and see (the bark beetles) ravaging beautiful trees. We even had to cut one down in our driveway."

A larger number of ponderosas were stricken last fall because drought-stressed trees are unable to repel the insect as it bores into the bark, Bob Celaya, forest health specialist for the Arizona State Land Department, said. "Coupled with the drought are overcrowded stands of ponderosa pine in these areas, all competing for the same limited moisture," he said.

Other factors that contributed to the problem include a mild winter in 1999-2000, which allowed a larger number of insects to survive; widespread breakage of ponderosa pines by snow, which provided an additional food source in Pine-Strawberry; and widespread construction activity, which provided large amounts of fresh pine debris and damaged and weakened remaining pines.

More than 2,000 species of bark beetles, which are also known as engraver beetles, have been identified. The one that affects the ponderosa pines in this area is known as the ips bark beetle.

"It's about the size of a match head, and it's shiny black to dark brown in color," Bob Celaya said. "A distinguishing feature is a noticeable depression at the rear end that is bordered on each side with three to six tooth-like spines."

Both the male and female ips bore into a tree and form an egg chamber. The spines are used to push red sawdust out of the tree as they go.

After the eggs hatch, the larvae bore out from the chamber, forming a series of tunnels. The early indications that a tree might be infested include piles of red sawdust at the base of the tree and soft pink to reddish-colored pitch tubes about one-quarter inch in diameter in the top one-third of larger trees.

"The damage starts in the top of the tree, in the crown," said Stevens. "It just gets brown, and then it slowly works its way down the whole tree and kills it."

But despite the destruction they cause, Celaya said people will probably never see an ips beetle unless they pry back the bark on an infested tree.

"Besides," he said, "the beetle is not the problem. The problem is the conditions that make the tree too weak to ward off an infestation."

It is important. Celaya said, to remove and properly dispose of dead trees if they pose a hazard to people, structures and vehicles. "It's also a good idea to cover diseased wood with a big plastic tarp once it's cut down so the bark beetles still inside die," said Cathy Stevens, who has attended workshops on how to deal with the pests.

"These beetles have wing covers and they can fly," Celaya said. "In fact they can fly for miles, and that's how they travel from one host to the next."

Celaya also recommends proper thinning of additional pines in overcrowded stands, which reduces the likelihood of future bark beetle mortality while reducing the chance of forest fire. He also suggests that property owners water valuable trees slowly and deeply in the late spring and early summer until the summer monsoons are well established, utilizing a soaker hose around the dripline of the tree.

From the deck behind Stevens' house, about 5 percent of the ponderosa pines in a forested area dotted with homes are either dead or have started dying from the top down.

"Since last summer it has gotten a lot worse," she said.

The fire hazard posed by the dead trees is one of Stevens' primary concerns.

"The trees that are goners need to be cut down a lot sooner than they have been," she said.

While the damage seems extensive, Celaya said the worst should be over, at least for the time being.

"Bark beetle activity should return to normal levels this year due to the cold temperatures and heavy moisture experienced this winter," he said.

Commenting has been disabled for this item.