Environment News

Protecting Our Oak Trees

With the start of spring and warmer temperatures there will be a noticeable increase in insects and the diseases that they carry. One that is of serious concern is the Gold Spotted Oak Borer (GSOB), which is a flathead borer that causes mortality to oak trees. Experts believe it was introduced into the Descano area of San Diego County by the transport of infested firewood from Southwestern Arizona in 2004. The GSOB mortality of oak trees has since spread to other portions of San Diego County as close as Julian and isolated areas of Idyllwild in Riverside County.

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 The Gold Spotted Oak Borer (GSOB) leaves visible evidence on three species of oak trees common in San Diego County. When their larvae create feeding galleries underneath the surface of the bark, GSOB attacks may be recognized by the following evidence:

  • Red or black staining in dime-sized to half foot sections
  • Blistering and oozing on the surface of the tree
  • Crown thinning
  • Twig and branch die-back

Evidence of injury can also include chipped outer bark from woodpeckers feeding on the larvae and small D-Shaped exit holes where the gold spotted beetles pupate and emerge from the tree. Impact varies between three oak species and can consist of gray or brown coloring in the crown of the tree and thinning of the foliage.

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Currently the Pesticide Program is using these monitoring tools to detect GSOB:

  • Putting up purple monitoring traps provided by United States Department of Forestry on oak trees in selected areas during the flight season from May through September to detect for GSOB.
  • Physical checking for symptoms of GSOB, implementation of an oak tree inventory, and numbering system.
  • Development of an aerial imagery oak tree map.

These are tips for how you can help prevent GSOB from being introduced into the community:

  • Check oak trees on your private property for symptoms of GSOB.
  • When you get firewood ensure that you check it and that it has been cured for at least 2 years.
  • Do not transport firewood from an infested area to an un-infested area.

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If  you have any questions or want more information contact Pala Environmental Department Pesticide Technician Jesse Castro at (760) 891-3549.

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