Hi Carl,

Thank you for your request for additional information regarding control of  your Red Turpentine Beetle infestation. Information is included below from UC IPM which provides information about Bark Beetle Control including the Red Turpentine Beetle.  The conclusion is that chemically treating trees that have been previously attacked is ineffective and provides no benefit. 

http://ipm.ucanr.edu/PMG/PESTNOTES/pn7421.html

They report that, ‘Unless trees are monitored regularly so that bark beetle attack can be detected early, any chemical spray application made once the beetles have aggregated and penetrated the bark is likely to be too late and ineffective. Treatment must target the adults by spraying the bark so that beetles are killed when they land on trees and attempt to bore into the bark to lay eggs. Chemically treating trees that have been previously attacked will provide no benefit and could kill beneficial insects. Seriously infested trees, or trees that are dead or dying due to previous beetle attacks, cannot be saved with insecticide treatments and should be removed. Systemic insecticides, meaning those that are implanted or injected through the bark or applied to soil beneath trees, have not been shown to prevent attack or control populations of bark beetles. Although new systemic products are being investigated, they are not currently recommended for bark beetle control.’