Insecticide Spraying Of Trees Shuts Down Crystal Lake Recreation Area

If you had plans to visit the Crystal Lake recreation area in the San Gabriel Mountains and Angeles National Forest this week, you should change them. Officials closed the area Tuesday to spray insecticide on pine trees to protect them from a tree-colonizing beetle.

The closure is set to end Sunday.

The western pine beetle is small, about 3 to 5 millimeters, but it can cause big damage to pine trees around this time of year. That's when the little brown bugs exit dead trees to find living ones to tunnel into and lay their larvae. Angeles Forest officials say drought and the western pine beetle have killed nearly 200 trees in the area.

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The U.S. Forest Service says tree deaths in recreational areas can create hazard trees, fire risk and threaten infrastructure.

The beetles aren’t all bad

Tim Paine studies pest management in forests at the University of California, Riverside. He said treating trees with insecticides in campgrounds and areas used by people is part of the Forest Service’s policy.

"The western pine beetle is a natural part of the forest," he said. "They're a vital part of that ecosystem — a problem from our perspective when they get to really high populations because they can kill large numbers of trees."

He said the beetles typically have to kill a tree to reproduce, but they usually target weak trees damaged by drought or lightning. Most of the time they're in the background, and we don't really notice them.

How to tell if a tree is infested

Paine said you can see several signs on an affected tree. One is called a pitch tube, which looks like a little dime-sized mountain with a hole in the center on the tree’s trunk.

Meanwhile, a tree trying to defend itself can release resin or pitch to try and kill the beetle.

But if a tree is badly stressed, Paine said red sawdust starts accumulating in the bark and the base of the tree.

"When that happens, typically the tree is under full attack and unable to defend itself,” Paine said.

"The tough part is that the tree stays green for a considerable amount of time," he said. "So if you're standing 10 or 15 feet away from the tree and you look at it and you don't see any pitch tubes, that doesn't necessarily mean it's not under attack."

Paine said the tree can take weeks or months to transform from green to red.

But the challenge is keeping the beetle population down. He said once the population gets high enough, there's a very high risk of tree death, and not a whole lot can be done.

"It's an all-or-none situation where either the beetles are successful at killing the tree or the tree's successful in killing the beetles," he said.

Should I be concerned?

Paine said the beetles can especially wreak havoc during drought years. In the early 2000s, pine trees in Big Bear, Crestline and Lake Arrowhead were devastated by them when rain totals were low — 1 in 3 pines died in the Southern California mountains.

But after two years of above-average rainfall, Paine said the trees should have enough water to fend off beetle attacks.

"When you think about it, many of these trees live hundreds and hundreds of years, so they are resistant — most of the time — to beetle activity," he said.