Infestation


Photo Illustration by Bryan Cole / The Collegian
Beetles, drought conditions threaten Afghan Pines and other trees in campus’ O’Neill Park

The Afghan Pine, like the ones that grow on the Fresno State campus, is a 30- to 40-foot evergreen tree with a fragrance that makes it an ideal at Christmas time. It has soft, short needles with sturdy branches that seem to stretch toward the sky. But lately, the branches of some of these trees in O’Neill Park have started to sag.

The now-brittle needles are showing more brown than green and the once-firm bark has taken on the consistency of Styrofoam.

Ryan McCaughey, the university’s manager of grounds and arboretum, said six to eight trees in the park are showing such symptoms. A few are already dead and will have to be removed.

The likely culprit: beetles.

McCaughey has seen emergence holes of a boring beetle underneath the bark, but it is still unclear which species is sinking its teeth into the wood.

There remains much speculation as to why the beetle threat has penetrated the campus within the last year.

“It’s very difficult to treat and [the infestation] is hard to get rid of without getting rid of all the trees,” McCaughey said.

Non-native species lures expert to campus

Beetle infestation of this degree is not common in California’s low altitudes like Fresno, but recent research headed up by the United States Department of Agriculture (USDA) Forest Service has found a fairly new and foreign species on the rise in urban areas that may hold the key.

Between 2006 and 2007, USDA forest scientist Steve Seybold studied such beetle infestations in the Central Valley.


Photo Illustration by McClatchy Tribune

He discovered that the Redhaired Pine Bark Beetle, a native of Europe, Russia and the Mediterranean region, had developed populations in places like Dinuba in Tulare County, attacking pine trees in parks, backyards and golf courses.

Known for the tiny reddish hairs on its wings, the Redhaired Pine Bark Beetle has few known natural enemies in California, making it particularly menacing.

When Seybold learned what Fresno State had on its hands, he paid the campus a visit.

Exploring the trees in O’Neill Park on Feb. 20, Seybold noticed emergence holes typical of a Longhorned Beetle, a 10- to 15-year California resident, in some of the trees. No beetles were found, however, and he said he couldn’t be sure of their presence until the higher branches were taken down and could be examined more closely.

“Typically when bark beetles are the cause of tree mortality, we see signs of their colonization at the base of the tree or at least at head height,” Seybold said.

Professor of entomology at UC Davis Mary Louise Flint, Ph.D., who contributed to Seybold’s research, suggested that Fresno State’s pest could also be the Mediterranean Pine Engraver beetle, another new inhabitant to California that’s been found as far north as Fresno.

“[The Mediterranean Pine Engraver] has been there for five or six years,” Flint said. “They do attack pretty much all the pines.”

Dehydrated trees more suceptible

Whatever the cause, there is reason to believe that drought conditions in California have made trees of all kinds more susceptible to parasites.

The state has experienced three years of below-average rainfall.

A similar lack of precipitation is believed to have led to the Mountain Beetle outbreak in Colorado that has depleted 1.5 million acres in the state since 1996.

“The really healthy trees are able to fend off attacks of the bark beetle,” said Flint, pointing out that bark beetles generally target trees that are weakened, often due to a lack of water.

This is especially true of the Afghan Pines in O’Neill Park that need well-drained, moist soil to build strong defenses against insects.

Pesticides can prevent attacks for a time, but the best solution, Flint suggested, is removing the trees that are infected.

McCaughey said 10 or 12 trees in the park will have to be cut down in the coming weeks at a cost of around $450 each.

Possible beetles, possible threats

No one knows which beetle is to blame for the deterioration in O’Neill Park, but a few particular species are strongly suspected to have infiltrated Fresno State.

• The Redhaired Pine Bark Beetle (Hylurgus ligniperda), a Mediterranean native about 5 to 6 millimeters long, was believed to have crossed the ocean to the U.S. in wood packing material. It was first sighted in November 2000 in New York and three years later in Los Angeles. It multiplies quickly, laying up to 500 eggs at a time in vertical galleries underneath the bark. It may complete two generations per year. USDA forest scientist Steve Seybold said scientists have not yet detected it anywhere north of Lancaster, Calif.

• The Mediterranean Pine Engraver, a native of the Mediterranean region and Central Asia (Orthotomicus erosus), was first caught in Fresno by the USDA in May 2004, but it has now been spotted all around the Central Valley. It can lay up to 75 eggs at a time and burrows just underneath the tree bark, creating an overlapping network of tunnels. It is 2 to 3 millimeters long.

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