Invasive Tree Beetle Monitoring and Detection

The City of Fremont will be initiating a monitoring program for a tiny, tree-damaging bark beetle called the Invasive Shothole Borer (ISHB). This non-native beetle is believed to have been introduced from Asia and was first detected in Southern California in 2012. ISHB has now recently been detected in neighboring Santa Clara County. ISHB introduces a fungus into the tree that causes decline, branch dieback, and eventually tree death. Common landscape trees like sycamore, cottonwood, sweetgum, trident maple, willow, and box elder are especially susceptible.

Regular monitoring is recommended by University of California Agriculture and Natural Resources to facilitate early detection of ISHB. The city will be installing sticky panel traps (see photo) in strategic locations on city property to monitor for activity.

What to look for in your own trees:

1. Tiny entry holes in the tree bark.  Perfectly round and less than 1mm wide (about the size of the tip of a medium ball-point pen).
2. Symptoms and signs accompanying entry holes.  Dark, wet staining, thick gumming, boring dust/frass (resembles fine saw dust).
3. Dieback. Dead branches with wilting leaves may be a sign of severe infection.

What you can do:

1. Keep your trees healthy. Proper irrigation and maintenance will increase your trees’ ability to protect itself from ISHB and other pests.
2. Check your tree. Look for the common signs and symptoms mentioned above.
3. Call a professional. A certified arborist would be able to assist with identification and management.

For more information about this beetle and management programs, visit the University of California Agriculture and Natural Resources ISHB website.  For more information on the City of Fremont Urban Forestry efforts please visit the City's Urban Forestry web page.