Help Save Our Trees in Pacific Palisades

Possible Infestation

In order to help stop the polyphagous shot hole borer beetle, UC Riverside’s Eskalen Lab suggests that residents keep an eye on their trees for signs of problems. The beetle’s entry holes are tiny and may be gummy, but they look different on different species of trees. Visit for examples of what infestations look like. The lab also requests that people send photos of possible infestations for analysis. Pictures should be taken with a pen pointed at the entry hole, and if the lab can’t determine whether the shot hole borer beetle is the cause, it will request a physical sample to analyze.

This dying box alder tree was infected by the fungus left by the shot hole borer. Photos: Eskalen Lab
This dying box alder tree was infected by the fungus left by the shot hole borer. Photos: Eskalen Lab

Help Gather Data

To help scientists track the presence of the shot hole borer, Rosi Dagit suggests that residents visit and learn how to create their own lures/traps. Once the traps, which mainly consist of two connected plastic drink bottles, are installed, citizen scientists can check for dead bugs and send their discoveries in for analysis. The more people who participate, the more accurately scientists can determine the spread of the beetle.

Stop the Spread of Bugs

Firewood purchased in one place and then taken to another on a camping trip, for example, can spread the beetle to new areas. In addition, don’t bring living plants from one area to another, as this also spreads insects to new areas.

When pruning, make sure to thoroughly clean the saw between trees so that pests or fungi aren’t spread from tree to tree.

Treating Infected Trees

If a tree is infected, it can sometimes be saved, depending on the severity and placement of the infection. For example, if only a branch is infected, the branch could be removed while the tree remains intact. Removal is often the safest option to save surrounding trees, but the dead wood must be disposed of properly so the beetles don’t spread. Big pieces should be either solarized under a clear tarp or disinfected by kiln drying. Visit for more information. 

Reduce the Impact

Plant more diverse trees, so that if a shot hole borer or other pest does invade an area, the loss of one species of tree won’t be so damaging to the canopy. View trees that are being considered by the U.S. Forest Service for drought-hardiness and potential pest resistance at

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