GOT OAKS? Let's keep it that way!


The Goldspotted Oak Borer (GSOB) is confirmed and killing oak trees near Lake Hodges. This is the beetle that has wiped out 100,000's of Oaks in Julian. The Beetle is also confirmed in Del Dios,  Mount Israel, Hidden Meadows, Daley Ranch, Penasquitos Canyon, and is predicted to be found in Elfin Forest and Harmony Grove.

Big healthy trees are dying of GSOB attack, often in one to two years. Oaks need effective care to resist this bark boring insect.

Prevention and control of wood destroying insects that live under tree bark is a challenging task that requires an integrated approach. Important activities include:

  • IDENTIFICATION: If you suspect golden spotted oak borer (GSOB) are infesting your oak trees and you live near the San Dieguito Watershed, contact  otherwise, contact University of California Cooperative extension:  
  • CONTAINMENT: Do not move firewood from your property or take it to other areas. Before spring begins, burn any remaining firewood from the previous season to eliminate the chance of the pests spreading to live trees. Studies of golden spotted oak borer populations have shown that infested firewood is a major source of new infestations and the expansion of the insect’s distribution.
  • TREATMENT: There are effective golden spotted oak borer control options using insecticides. Since insecticides must be applied at the right time and in strict accordance with the product label, always contact your pest management professional before attempting do-it-yourself control methods.

Coast Live Oaks have little or no natural resistance to this pest. Death of infested trees is above 80 percent unless managed for gold spotted borer control. The negative effects of golden spotted oak borer infestations don’t end with the loss of shade and beauty. Dead trees must be removed, per fire ordinance, and the service is costly.

The beetle's life cycle has been well studied, and its movement has been assisted by people moving oak firewood. Click here for more information about GSOB and firewood

Disrupting the GSOB lifecycle depends on preventing the emergence of adult beetles and/or new larvae entering the tree though it bark. This is done with a barrier pesticide on the trunk of the tree. Treatment must be timed correctly to be effective.

It is possible to protect high value oaks from this deadly invasive beetle with arborist pesticide treatment.

It is recommended to have your trees evaluated annually or you are gambling with your tree’s health.

2018 Summary and Update on GSOB Activity:

As most of you know GSOB is in its early stages in Del Dios and is already virulent in the Mt Israel valley.

Most of our Oaks are suffering from drought stress from our hot summer and late rains. Oaks are tough and can handle many stressors that mother nature dishes out.  However, GSOB is a non-native beetle that weakens the vascular system of these massive, life supporting living organisms and can kill a tree quickly.

You may see people poking around Del Dios collecting data about our oak trees. This accurate, eyes on the tree data is one of the Best Management Practices used to treat GSOB effectively. Our GSOB treatment plan focuses on spraying the trunk and thick branches of the oaks before adult beetles emerge. We are scheduling treatment in mid April.

A meeting with Plant Care Specialist, Ricardo Agular, is scheduled for March 21st at 6 PM in Del Dios Park. You'll have the opportunity to ask questions, learn about the signs of infestation, treatment and horticultural best practices. 

We have formed The 2018 'Healthy Oaks Club' as A way for Residents to act as Stewards of the Oaks.

--We are working with Aguilar Plant Care

--Treatment is scheduled for 2nd week of April 2018.

-- We have negotiated low rate for treating residential oak trees as a block of customers. For more information on having your oaks treated, contact



Tel: (760) 705-5571


Read: How to recognize a less than healthy oak tree

The Habitat Protection League is holding  an "Ask the Practitioner" Q&A session March 21st, 6:00 PM Del Dios Park with Ricardo Aguilar, Aguilar Plant Care. 

Bring a Sample - make it personal -

We welcome you bringing a picture or sample of the bark or leaves from oak trees on your property that you think might be infested.  Can't attend the meeting? Email your photos and comments to Susan at

Articles and documents for GSOB identification and management:


GSOB Natural History Management (3.3 MB)

Management Practices for Preventing the Spread of GSOB

GSOB Field Identification Guide (5.3 MB)

GSOB Information & Updates