Pest Control

GSOB Map - March 2018

The following map images show oak tree evaluation results through March, 2018.

You may also download a pdf image of the full map.


Each dot represents an oak tree. Color legend:

Red = GSOB confirmed, High Risk

Orange = GSOB confirmed, Lower Risk

Green = Healthy

Yellow = Problem Tree, no GSOB

Purple w/ Black Outline = Removal Candidate

Click images to enlarge.




GSOB Update: March 2018

GSOB Update

As most of you know GSOB is in its early stages in Del Dios and is already virulent in the Mt Israel valley. In Spring 2017 Brett Hutchinson meet with 40 residents in Mt Israel to show us bugs, canopy assessment, D shaped exit holes and a whole road show. The week before the Habitat Protection League hosted 85 people at a firehouse meeting with Dr. Tom Scott, UC Riverside, and Kevin Turner of Cal Fire.

Winter 2018: 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. What makes it hard are the extra things that humans add to the mix: grading, hardscapes, watering or planting schemes that may suit fungus more than oak tree roots, and non-native insects. Most stressor are slow acting. However, GSOB weakens the vascular system of these massive, life supporting living organisms and can kill a tree in a couple years.

You may see either Rob or Stacy McCline (and more volunteers - come help us!) poking around Del Dios collecting data about our oak trees. This accurate, eyes on the tree on data is one of the Best Management Practices used to treat GSOB conservatively and 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 and who to contact to have your trees effectively treated. Sign up for our newsletter or follow us on Facebook for updates to the meeting schedule. 


Bring a Sample

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

GSOB Facts

• Crown thinning, not dead branches, suggests GSOB infestation.

• An attacked oak won’t last long once it looks bad. Big trees usually die quickly.

• An oak can withstand GSOB attack for 1-15 years before dying. Factors include: health, drought, size, rot and level of insect attack. 

• GSOB is spreading.
– By movement of infected firewood.
– Dispersal of beetles primarily within an oak canopy.

• There is no cure for GSOB.
– No biological control is being attempted. The natural predator is a parasitic wasp, but UCRiverside couldn’t get it to breed.
– Not an Agricultural threat so not much funding is available to study the pest.

• No existing template available for addressing conservation lands or ecologically significant woodlands. Best management practices are applied for each situation.

• Cal Fire grants are available to remove trees, not to save them.

One of our local residents, Diana Short, had her trees treated last year. Here's what she had to say about her experience. 

"I have enjoyed learning about this beetle this year. It is not my favorite insect, for sure. To protect the oaks on "my" property we had a professional team visit and they gave us a topical spraying recommendation based on the size, age, and species of oaks. The cost was less than I had anticipated because I counted all the oaks, even the very young (less than 12" diameter), which are less at risk, apparently and didn't need treatment. Of the four trees sprayed, there is only one that is not doing so hot. Before spraying we identified the little black "D" s on the trunk and saw that it was not as verdant as others. It might make it- we hope for the best. This season I will be spraying early to hopefully thwart further damage. I am no expert, but when I'm out walking in the neighborhood I try to observe the general health of the local oaks. Most look good. I hope our oaks outlive this unwelcome beetle, and that this small act of tree care saves their lives."

Latest GSOB Posts

How to Recognize a Less Than Healthy Oak Tree

Stand near the trunk of your tree and look up into the canopy. Crown thinning and dying branches are often the indicator of a GSOB infestation. A healthy Oak will exhibit full thick leaves at the top, but as infestation occurs and progresses, branches and leaves will begin to die and thin. Another beetle (usually the western oak bark beetle) attacks drought stressed trees at in the upper branches. 

Learning to differentiate details about your oak's canopy and trunk are key to evaluating your trees. Doing this at least annually allows one to have enough time to respond and best care for your oaks, before the infestation becomes critical to the tree's health.

Got Oaks? (Maybe) Not for Long - MEETING JUNE 7th

GSOB Killing Trees in the Del.jpg

Help Save Our Oak Trees

GSOB has been confirmed in Del Dios & Mt Israel

Join us Wednesday June 7th
6:30-8:30 pm
at the Old Del Dios Fire House

20155 Elm Lane

If you love our community oak trees, please come to an expert panel presentation. GSOB, Golden Spotted Oak Borer, has now reached Escondido. This is the beetle devastating the oaks in Julian and much of East County. Since its discovery in 2008, GSOB is responsible for the death of over 100,000 oak trees in San Diego County, with the number growing every day.
What can we do to save our trees? Education, early detection and response is key to managing the health of the oak trees. Come hear the best available science and management practices from state level experts: 

  • Dr. Tom Scott:  UC Riverside - Conservation Biologist and primary research associate on GSOB for 8+ years
  • Kevin Turner Southern California Invasive Pest Coordinator, Department of Forestry and Fire Protection Kevin holds the reins on addressing the devastation this insect brings to our oaks. 

In researching GSOB, there are many opinions about what can and cannot be done.  Some say nothing can be done – just let the trees die and contain the wood on site to prevent the further spread of GSOB.  Others suggest using good horticulture, chemical sprays, tree injections and even herbal teas. This leaflet link is the most current and definitive source on GSOB:
Further information and a Hands On work shop with professional arborist will happen later in June. 
See our GSOB Information & Updates page for more information.
Stacy McCline
President and Founder
Del Dios Habitat Protection League