California’s oak trees are facing another challenge to their survival. The gold-spotted oak borer (GSOB) was identified in California in 2006; since that time, over 17,000 oaks have died from this pest.

The loss of oak trees, especially in the wild, brings many negative impacts: loss of wildlife habitat, greater risk of erosion and catastrophic fire, invasion of noxious weeds, as well as safety risks related to falling trees or branches.

The borer attacks the trunks and branches of mature oaks. While most pests attack trees that are stressed or weakened, the GSOB attacks large, healthy trees – including trees in yards.  Thus far the damage has been contained to San Diego County.

Much work is being conducted in an effort to learn more about the GSOB. With more knowledge, researchers hope to be able to stop the destruction of these magnificent trees. At this time, all we can do is work together to slow the spread of the GSOB with the following steps:

• Do not transport oak firewood into or out of campgrounds or parks
• Chip infested oak wood to 1-inch pieces
• Cover stored oak firewood with 6 mm, UV-stabilized, durable plastic tarps in the spring. Secure all the edges of the tarp to the ground to prevent beetles from escaping
• Season oak firewood. Remove the bark and place the wood in direct sunlight

Pictures of the borer, the damage caused, and more information can be found here.

Mark Bolda is the Strawberry and Caneberry Farm Advisor in Santa Cruz, Monterey and San Benito Counties.  Our own Oleg Daugovish collaborates regularly with him on many projects.

I would like to share with you Mark Bolda’s blog. He has several posts related to the spotted wing drosophila (SWD) previously known as the cherry vinegar fly. These posts include:

• the importance of monitoring for this pest allows growers to manage the insect before the infestation is heavy
• what to look for and steps to take if found

In addition to being informative, the posts on SWD that span about one year are additionally interesting as they are written as the problem unfolds.  It is a glimpse into the on-going work and the on-the-ground problem solving that comes with being a UCCE Farm Advisor.

I am sorry to have to report that we have another potential ecological and economic disaster coming our way. Much like the Asian Citrus Psyllid and Huanglongbing disease, this new threat is also a pest-disease complex.

Laurel Wilt Disease (LW) is caused by a fungus, which is carried by the Redbay Ambrosia Beetle (RAB). These beetles typically attack trees under stress (e.g. drought). The beetle bores into a tree carrying the fungus. The fungus in turn digests the wood disrupting the flow of water and nutrients.  As the tree weakens it becomes more attractive to the RAB and is used for brood rearing and is attacked in mass. It only takes one beetle to cause the infection. Once a tree is infected it takes about 6 months to collapse. Unfortunately one of the hosts for the RAB is the avocado tree.

The initial detection of this disease in the US was found May 2002 in Port Wentworth (Savannah), Georgia. It has spread mainly along the coast of South Carolina, Georgia and Florida as of 2008.  It is currently in the avocado orchards around Miami.

Much research is being done to help stop this destructive disease. While resistant trees are the subject of much of the research, we can all do our part to help stop the spread of the disease. This can be done in the following ways:

• Report any suspicious laurel trees to CDFA
• Voluntarily remove and destroy the tree
• Don’t move any symptomatic host wood from a site
• Don’t chip dead wood and use it as mulch around the yard
• For now, don’t purchase or obtain native Lauracae plants and avocado trees from an area known positive for the RAB-LW
• Leaving the tree in place will increase the RAB-LW infestations throughout your local area.
• Controlling the beetle may be impractical in the home landscape – it only takes 1 beetle to infest a tree.

Current control strategies are as follows:

Options for dooryard avocado trees

• Cut and burn the tree – not recommended because of the danger of burning and the requirement for burn permits, and various ordinances of local, state and federal agencies.
• Cut the tree down to the ground.
  • Pile the wood or chip the wood of the tree, pile it on top of the tree stump and tarp this pile of wood to the ground; essentially composting the infested remains of the tree in-place
  • Adding biosolids (e.g., manure), fertilizer, and water will speed the decomposition process
  • Spray your chainsaws with bleach and water to disinfect it against the possibility of spreading LW fungus to other susceptible host trees.

There have been two earlier posting on this blog about the Asian Citrus Psyllid (ACP)and the potential crippling impact for citrus in California caused by the Huanglongbing vector (aka citrus greening disease) this insect carries. Please read the Introduction to the Asian Citrus Psyllid and Asian Citrus Psyllid: Lessons from Florida for additional information about this pest.

We are entering the time of year in which the ACP becomes most active. Make sure to check your trees regularly for signs of this insect. The Introduction to the Asian Citrus Psyllid post provides detailed photos and descriptions of how to determine if this species is on your trees. If you see this psyllid, call the California Department of Food and Agriculture at 1-800-491-1899 right away.

I recently asked Ventura County UCCE Farm Advisor Ben Faber what I should share about the ACP. He said to remind people how important it is to make sure to declare plant items when crossing the border. It is people who are spreading this around.

Recently UC Agriculture and Natural Resources’ News and Information group released a video demonstrating for the general public how to detect Asian Citrus psyllids on their garden trees. The video is available at:

http://news.ucanr.org/newsstorymain.cfm?story=1233

In addition, our office has a supply of bookmarks that contain photos and instructions for identifying both ACP and trees struck by Huanglongbing. They are available in both English and Spanish. Please contact our office if you would like some.

ACP infestation

ACP feeding damage

Distorted leaves from ACP