In order to avoid superfluous sprayings, i wouls suggest to prune the trees and get rid of the "dead wood". I would send a saqmple of branches with the fungus bu aslo some green shoots to a Plant Clinic for the identification of the primary agent of the dye back, The primary casue doesn't necessarily have to be a parasitic such as a fungal agent. The present fungus could be a saprophyte that develops on affected tissue. Thus, would check whether the trees are properly irigated and fertilized. It would be reasonable to invite an extension plant pathologist or a private advisor to look at the trees if the pruning and improved treatments wouldn't resolve the problem.
