Types

• Several types of borers cause problems with evergreens. These include weevils, bark beetles such as the southern pine beetle and black turpentine beetle and caterpillars such as clearwing borers and carpenterworms. Roundheaded borers -- which come from longhorned beetles -- do more damage than flatheaded borers, but feed on dead and dying trees, rather than healthy trees.
  
  

Signs

• Signs of infestation by borers include holes in the bark and tunnels in the wood of your evergreen, the presence of excrement or frass and sawdust piles from tunneling, dead or dying foliage and noise of the borers chewing away inside the trees. Evergreens offer tree owners a slight advantage in detecting the presence of borers, as pitch may seep from the holes they create. The presence of pitch alone is not indicative of an infestation. You must remove the pitch to look for holes.
  
  

Prevention

• Maintaining healthy trees through good care and maintenance is one of the best ways to prevent borers. Select evergreen trees that are resistant to borers when possible. Reduce stress on your trees by placing them in a location that best meets their needs. Protect vulnerable trees against damage and wounding. You shouldn't prune when the adult-stage borer pests are present and active.
  
  

Treatment

• Attempt to identify the borer causing the infestation to make an informed decision regarding whether the affected trees should be removed to prevent pests from spreading. The type of borer, stage of infestation and severity of infestation are all considerations in treatment, and the proper timing of insecticide applications is very important. Insecticide treatments have to cover the entire tree to be effective, as the insects have to come into contact with the insecticide for it to be effective. In heavy infestations, the trees may be lost because of the difficulty of covering all the main limbs and trunk surface. Insecticide injections and implants are available to treat for pests that feed in the shallow layers of trees, but these should be introduced by professionals. Such treatments are not as successful in evergreens because pitch fills and blocks the injection sites.