Entomologist says Sierra Bark beetle epidemic will last as long as the drought

In a scene becoming commonplace throughout Calaveras County, two of four dead ponderosa pines in Arnold earlier this month were trimmed and waiting to be cut down.

Ponderosa pines are the chosen victims of the western pine beetle and the trees are going to continue to die at an alarming rate along the western slope of the Sierra Nevada until either the drought is over or the trees are gone, a U.S. Forest Service research entomologist said Thursday.

Christopher Fettig said in an interview on Calaveras Public Access Television that the outbreak of western pine beetles could become one the fifth most-profound infestations in modern history.

“This could become one of the largest outbreaks in the past 100 years or so,” Fettig said. “But these outbreaks usually last two or three years, or until there are no more hosts for the beetle to attack.”

He cited as a model an outbreak of the western pine beetle in the San Bernardino Mountains in 2003. “That was over once there were no more live ponderosas for the beetles to colonize,” he said.

The western pine beetle is a boring insect about the size of a grain of cooked rice. Fettig said there are thousands of species of bark beetle and nearly 200 species in California, but it is the western pine beetle and its particular relationship with ponderosa pine trees that is causing what may soon become one of the largest beetle infestations.

“This is an epidemic,” he said. Dense western forests and a drought that is as profound as any in recent memory have combined to create an ideal situation for a beetle explosion.

The western slope of the Sierra is filled with tightly packed forests and a thick understory of brush. In these conditions, in times of no drought, the trees successfully compete for water and, while their health might be marginal, they continue to survive. But when a drought comes, water is limited or removed and the normal process that keeps beetles at bay is removed.

The western pine beetle, and all of the other beetle species, are native and an important part of the ecology, Fettig explained. But the system becomes unbalanced when drought and overcrowding are present.

He said the pressure of sap inside the tree normally pushes the beetles out as they try to set up colonies. When water is missing, the interior pressure of the tree drops and beetle colonies multiply unhindered.

In California, the landscape that has suffered most in the drought is the area along the western slope in elevations from approximately 3,000 feet to 6,000 feet. Mortality in this elevation becomes more apparent each week, as more and more ponderosa pines show physical signs of stress and impending death.

Fettig said the first signs of beetle infestation are discoloration in the needles, usually at the tops of the trees. Pitch tubes, runs of yellow pine pitch coursing down the side of tree come next, then once the trees is dead, there will be piles of sawdust at the base of the tree.

He said the chances of saving a beetle-attacked tree are slim. Fettig said there are insecticides that can be used, but the success with them is marginal. Many of the chemicals that can be used, however, must be applied by certified pesticide applicator.

The best protection against beetle attacks is prevention. The natural state of the Sierra forest – what has evolved over millions of years – are stands of big trees spaced far apart, with no brush understory. Removing brush and cutting out weak and cluttered trees will provide a healthy habitat for the remaining trees and they will experience reduced competition for limited resources.

The complete Inside View interview between Fettig and moderator Enterprise Editor Dana Nichols can be seen on Calaveras Public Access Television beginning Friday at 7:30 a.m. The program also becomes available for viewing on CCTV’s YouTube channel.


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