Urgent Pest Alert: Invasive Shot Hole Borer Reaches Northern California A new threat has emerged in Northern California's forests and urban landscapes.

 Urgent Pest Alert: Invasive Shot Hole Borer Reaches Northern California

A new threat has emerged in Northern California's forests and urban landscapes. This new Invasive Shot Hole Borer (ISHB), is a highly aggressive non-native ambrosia beetle, and has been detected in Felton, CA. This discovery marks a concerning northward expansion of the pest from Southern California, where it has already caused devastating damage to millions of trees.

Understanding the Threat

This latest shothole beetle-pathogen complex (Euwallacea interjectus-Fusarium floridanum), originally from Southeast Asia, poses a severe risk to our Central Coast regions through a two-pronged attack:

Boring Damage

Beetle boring galleries

Adult beetles create extensive damage by constructing reproductive galleries within the tree's vascular system to lay their eggs. These tunnels directly compromise the tree's ability to transport water and nutrients.

Fungal Infection

Perhaps more dangerous is the beetle's relationship with the Fusarium fungus. Female beetles intentionally inoculate their galleries with this pathogen, which serves as food for both adults and larvae. The resulting condition, known as Fusarium dieback, progressively destroys the tree's vascular system, ultimately leading to death if left untreated.

What makes this pest particularly concerning is that a single beetle can initiate an infection that spreads to other trees, creating a cascade effect of forest destruction.

Identifying an Infestation

Hundreds of beetle hits.

Early detection is crucial for controlling ISHB spread. Tree owners should conduct regular inspections, particularly during the beetle's active "fly out periods":

• Spring: March-April (approximate)

• Fall: September through November

Look for these key signs:

• Entry/exit holes about the size of a ballpoint pen tip

• Wet staining on bark

• Gumming or sugary buildup

• Presence of whitish sawdust

Advanced ISHB infestation and foamy canker expression. Most likely from oak bark beetle

Taking Action

If you suspect an Invasive Shot Hole Borer infestation, immediate action is critical. Trees can often be saved through targeted applications of insecticides and fungicides, (when necessary) if the infestation is caught early enough. However, severely infected trees may need to be removed promptly to prevent them from becoming breeding grounds for these pests.

The Road Ahead

While California has dealt with shothole borers before, this Polyphagous variant represents an unprecedented threat level in terms of tree mortality rates. At Tree Solutions, we've observed increased borer activity over the past 24 months and have already successfully treated several cases, including a native sycamore in Felton.

Throughout 2025, we will be working closely with the Agriculture Department, submitting samples for official confirmation and monitoring of this emerging threat.

Protect Your Trees

Don't wait until it's too late. Contact Tree Solutions, Inc. to schedule an assessment with a certified arborist who can evaluate your trees and provide management recommendations. As licensed providers for both tree care and pesticide applications, we're equipped to help protect your valuable trees from this emerging threat.

Tree Solutions, Inc. is fully licensed for tree pruning, removal, and pesticide applications. Contact us today for professional assistance in managing ISHB and other tree health concerns.

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