I assume that you are asking about the Mediterranean oak borer that has recently invaded some areas in Oregon. If that is the case, there is not yet a well-tested treatment to protect mature oak trees. Application of systemic insecticides may be an option, but further testing is needed to confirm this. Entomologists and other tree experts are currently studying and testing practices and treatments for prevention and protection. For more information, please see the fact sheet on Mediterranean oak borer at https://www.oregon.gov/odf/Documents/forestbenefits/fact-sheet-mediterranean-oak-borer.pdf