I talked to Dr. Steve Frank, an Entomologist working on Ambrosia Beetles, today on the injury and pest pressure many growers are facing from Ambrosia Beetles. Below I have included the link to 2 articles that he has written to help mange this pest through trapping and control measures, products and timing. As a Horticulturist, I will try my best to briefly summarize our discussion. From their research, unstressed trees are unlikely to be affected by Ambrosia Beetles.
If that is the case, why are we seeing significant damage in some areas this year? Stress!
One of the leading issues they see creating stress in nurseries preceding damage is water saturated soils or winter damaged trees. We also discussed the frost/freeze damage this year where new growth had emerged and was killed by the frost which would release "scents" that the insects could key in on as an indicator of plant stress. So in orchards where damage is being seen, I would suggest evaluating the situation to identify sources of stress. Although nothing can be done for the already damaged trees, it is critical to minimize stress going forward to prevent future damage.
Hope this helps to clarify the issue a bit and provide information on managing this pest from the expert!
Dr. Mike Parker
The link to the Ambrosia Beetle articles can be found at: