Bark Beetle

Tom Coleman, forest entomologist for the U.S. Forest Service, chips away at the bark on a Jeffrey Pine to look for Bark Beetles in the Barton Flats area of the San Bernardino National Forest in May. (Sarah Alvarado — Staff photographer)

By Jim Steinberg, The Sun
Posted: 06/13/15 – 9:51 PM PDT |

They are insects the size of rice grains, with miniscule mandibles that bring down forests.

Now and for the next several weeks, these tiny tubular timber terrorists are expanding their footholds in the forests of California as they fly out of dead or dying trees to find this season’s hosts.

The proliferation of bark beetles in the Western United States forests “is the largest insect outbreak in the history of the planet … at least in recorded history,” said Diana L. Six, professor of forest entomology and pathology at The University of Montana in Missoula, Montana.

The bark beetle population boom is especially concerning in California, which is in its fourth year of extreme drought.

In the San Bernardino Mountains, stands of dead or dying pine trees are visible for the first time in the current drought, said Tom W. Coleman, an NFS entomologist for the Angeles, San Bernardino, Cleveland and Las Padres national forests.

Bark beetles and tree die-offs are part of an equation which equals higher fire risk for the Southern California forests this fire season over last year.

“We are worse (this year) in terms of fuels,” said Rob Krohn, a meteorologist with the National Forest Service’s Southern California Predictive Services Unit in Riverside.

This fuel mix includes both the dead trees of the bark beetle’s voracious invasion and dead stands of chaparral and chamise. These bushes grew vigorously following the heavy December rains, but have died in the dry heat since then, he said.

Bark beetles appear to be at record levels in the state’s Central Coast and Southern Sierra ranges, said Jeffrey Moore, a National Forest biological scientist based in Davis.

Bark beetle populations are so high in some areas that they “will continue to kill huge numbers of trees even if the drought ends. Furthermore, if the drought continues, tree mortality will likely continue to accelerate,” Moore said.

Although the increase is not as dramatic in the four national forests of Southern California, populations are rising as the drought enters its fourth year, said Moore, who directs the NFS’ California aerial survey program.

Earlier this spring, an aerial survey of Southern California forests showed that about 2 million trees have been killed by the bark beetle, leaving 164,000 acres scarred with mostly dead trees.

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