What are invasive shot hole borers?

ISHB are small beetles that carry a fungus, called Fusarium, which can kill trees. These pests are about the size of a sesame seed. They bore small holes, roughly the same size as the tip of a ballpoint pen, into trees and spread the fungus. This can result in a severely damaged or dead tree, if not cared for properly.

What is the City doing to manage infestation?

Our Forestry team and Americorps volunteers, who are working with Our City Forest, have started to inspect trees. They are determining how many trees are infested and how badly. After they finish inspection, they will know how many trees require treatment. Select trees that are moderately infested will be injected with a fungicide and an insecticide in spring 2025. Our Forestry team is waiting until spring to treat these trees, when they can draw in the treatment better while they are experiencing spring growth.

In the meantime, our Forestry team will continue to monitor and map out infested trees. They also plan to leave doorhangers in affected neighborhoods, so they can speak with property owners about ISHB infestation.

How can I spot ISHB and what can I do about it?

A few telltale signs of infestation are large brown marks, entry holes, and thick gumming on tree trunks. If you suspect signs of ISHB infestation, don’t panic! We recommend that you get ahold of our Forestry team by:

• Calling 408-794-1901
• Emailing arborist@sanjoseca.gov
• Or, you can fill out our online form to report an infestation, and don’t forget to include a photo

^{A sycamore tree infested by invasive shot hole borers.}

We also plan to host two virtual information sessions in early 2025. You’ll be able to learn more about ISHB and chat with arborists. Visit the ISHB webpage to sign up for one of the sessions.