|Dead, dying, and diseased oaks are a problem in San Diego
County. The Gold Spotted Oak Borer is here. Don't move oak wood anywhere in the county.
|San Diego, CA- August 31, 2009…The gold-spotted oak borer is a newly
detected insect pest that affects California black oaks, coast live oaks, and
canyon live oaks in southern California, and which is believed to be responsible
for significant tree mortality in San Diego County. Over 17 thousand trees have
been killed across 28 thousand acres in and around the communities of
Descanso, Guatay and Pine Valley. Federal, state, and local officials are taking
action now, while the oak borer infestation still covers only a portion of the
county, in hopes of reducing the scope of the insect's spread. Indicators that a
tree may be infested include crown thinning, the beginning of significant leaf
dropping, and die-back of twigs.
A Web site has been created to provide further information about local resources
and a map of the infested areas. Instructions on how to send a sample from a
tree that may be infested by the oak borer to the County of San Diego
Department of Agriculture, Weights and Measures is included. For information,
please visit: http://ucanr.edu/sites/gsobinfo/.
Officials have not yet determined a way to stop the spread of the oak borer
completely. However, community members are requested to do three things to
help limit the spread of the oak borer throughout the county and reduce the
chances that more oaks will die on private and public lands:
Stopping the transportation of oak firewood is important because the oak borer
typically lays its eggs in bark crevices. The larvae grow to be 18 mm long and 3
mm wide. As they grow and feed, the larvae dig into the tree, creating tunnels--or
"galleries"--on the surface of the sapwood. These feeding habits kill sections of a
tree and, over a period of a few years, the entire tree itself. As they mature, the
oak borers leave the tree by making D-shaped exit holes about 3 mm wide. The
oak borers are compact and bullet-shaped. They can be identified easily by their
dull, metallic green color and the three golden spots that are located on each wing.
- Do not transport oak firewood into or out of campgrounds or parks.
- Leave oak firewood at home and use local sources of firewood when you
camp or have picnics.
- When you use local oak firewood, leave any unburned wood on-site when
you return home.
The following three methods can be used to help reduce potential oak borer
populations in dead and/or dying trees. These methods are listed in decreasing
order of effectiveness.
- Chip infested material: Chipping infested oak wood to one-inch pieces is the
best method for eliminating oak borer populations.
- Cover infested wood: If oak firewood cannot be chipped, cover the wood
with 6 mm, UV-stabilized, durable plastic tarps beginning in the spring. Tarps
should be used until the end of September. Pin or otherwise secure all the
edges of the tarp to the ground to prevent beetles from escaping. It is best to
tarp oak firewood piles in continual direct sunlight with a southern exposure.
Check the tarp periodically to ensure that it does not shred and therefore allow
escape routes for the oak borers.
- Season oak firewood with bark removed in direct sunlight: Scatter oak
firewood in areas in direct sunlight, preferably with a southern exposure, for an
entire growing season. Cut or split large pieces of wood into smaller pieces to
enhance drying. Removing and destroying the bark also can facilitate control
of the oak borer. Turn over the firewood monthly to expose all edges to direct
For more information and local resources please go to http://ucanr.edu/sites/gsobinfo/.