GOT OAKS? Let's keep it that way!

April 15, 2019

Our oak trees are looking good - the wet winter has helped encourage verdant new growth. As members of the healthy Oaks club know firsthand, Del Dios would be on track to experience the same devastation visited on Julian and Mt Israel without our early detection of the Golden Spotted Oak Borer (GSOB) and selective treatment. This year nearly 40 residences have had their oak trees treated by Aguilar Plant Care at a discounted group rate.

We are seeing the treatment working. No oaks we are treating have died. In contrast, a handful of oaks that were not treated are showing symptoms of decline and have started treatment this year. In keeping with best management practices, oaks are monitored by Del Dios Habitat Protection League volunteers. Annual inspection shows that the severely damaged trees are improving, based on measured criteria, like oozing sap and canopy density.

The City of San Diego has partnered with the League to implement a plan for protecting the oaks on City property. They contracted with Green Tree Forest Service, a leading company who worked extensively with the University of California researchers developing treatment methods for GSOB. Green Tree has been treating oaks in Julian and greater San Diego County for the past decade, as well as being hosted in 2017 by our League to give a talk to the community. Green Tree will be treating infected trees on affected properties along the Lake and into the neighborhood of Del Dios. Treatments are expected to occur May 7-10 this year.

May 12, 2018

Good News!

City of San Diego Public Utilities Department has contracted with Green Tree Forest Service to treat our local high value oak trees against GSOB (Golden Spotted Oak Borer) attack. GSOB is the beetle that has devastated the forests of Julian and has been found here in Del Dios. The DDHPL has mapped and evaluated the health of our Del Dios oak trees and this information has been used to determine which trees to treat. Many home owners in Del Dios elected to treated their trees this April as part of our Healthy Oaks campaign.

Green Tree Forest Service is scheduled to begin on May 21 and plan to be complete by May 25. Areas where trees are going to be treated will be posted a minimum of 24 hrs prior to treatment and extra personnel will be present to direct the public away from active work areas.

Please contact John Barone via email: or phone (619) 533-6641 with any questions or concerns.

Thank you, City of San Diego Public Utilities department, and our Healthy Oaks advocates for your continuing support.



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.


DDHPL GSOB Tree Inventory - mid town.jpg




--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

Aguilar Plant Care is a GSOB specialist company with the specific knowledge and professional licencing to do these treatments and effectively and appropriately.


Tel: (760) 705-5571

Prevention and control

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 from April through May, depending on weather conditions.

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