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Julie Maxey-Allison | 10th Street

Bark Beetle traps in
Seagrove Park.
Photo Julie Maxey-Allison.
Click to enlarge.

They are out there. Though you can’t see them, bark beetles are hungrily feasting on and are killing our Torrey Pines, and other trees.

These small, hard-bodied insects, the size of a grain of rice, generally dark red, brown, or black, sport jaws just made to chomp through a tree’s outer bark. Once they gain an entrance into the tree trunk they colonize the interior area. The females lay eggs creating “larval galleries.” Then, they all feed off the moist inner bark, the phloem, thereby cutting off the tree’s ability to distribute nutrients and produce the protective resin they use to ward off predators. Eventually the tree’s needles and limbs turn a death rattle rusty brown. The beetles simply squat in dying trees and use them as breeding nurseries, in fact emitting a pheromone—a chemical they use to communicate and attract others to produce more of their kind to spread to and invade nearby trees.

California now counts 20 invasive species of bark beetles, some new to town, arriving after 2002. You can spot them by a scattershot pattern of holes on a tree’s outer bark. They may be the engraver beetle, the red turpentine beetle or both. Our trees are especially vulnerable now because of drought. While a healthy tree can resist infestation with resin that pushes out the invaders, drought-stressed trees aren’t able to manufacture adequate amounts of resin to repel the beetles.

The best prevention against a bark beetle attack is to keep your trees healthy, including the root system. In times of severe drought, water the tree early in the growing season, saturating the soil down to two feet near the outer edge of the branches.

It’s tough to de-bug. If you notice rusted branches, immediately check for, remove and destroy any infested trees to halt the assault of the raider beetles. Do the same for any damaged green material larger than three inches in diameter. There are several possible ways to stop initial attacks from becoming more severe and to discourage the beetles, including chemical sprays and injections that may provide protection. Of course, the effectiveness of any treatment will be determined by the specific conditions of the tree—the depth and severity of the destruction to date. To learn more about how to defend against and rid your terrain of bark beetles go to The City of Del Mar website: delmar.ca.us and search bark beetles.


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