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

 Urgent Pest Alert: Three Invasive Shot Hole Borer species Reach Northern California

A new threat has emerged in Northern California's forests and urban landscapes. Two highly aggressive non-native ambrosia beetles (Invasive Shot Hole Borer), have migrated northward from Souther California. A new recently discovered species in Felton, California brings the number to three.

The northward expansion of the beetle's territory and the real potential of another aggressive beetle which is currently moving northward from the Cleveland Forest near San Diego is alarming. Together they have already caused devastating damage to millions of trees.

New beetle discovery in Felton, California

During the fall season of 2024, a new species of shothole borer (Euwallacea interjectus) was discovered in Felton, California. The damage to trees in a nearby riparian area is quite extensive. (Pics coming soon.) Boxelder tree (Acer negundo) damage is very extensive, killing most of the creekside native tree inventory we observed. Damage to the Magestic California sycamore, (Platanus racemosa) is growing. It appears that we may lose these trees too unless atreatment plan is initiated . To date, proven effective pesticide treatments are not allowed due to proximity to the creek and the protections in place to protect native aquatic species. We are hoping an exception will be put in place, allowing the careful use of pesticides will be approved before we lose this tree inventory. The potential consequences are devastating. The same issue is occuring in City of San Jose riparian areas.

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 trees 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. or another qualified tree service in your area to schedule an assessment. We recommend you an experienced certified arborist to 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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