I have had die back of branches, stems and leaves on my apple and pear trees for 10 years now. Originally they were doing well but after about 5 years the die back started to happen. The drainage around the trees can be problematic, it can get very wet after prolonged rain but the symptoms only started a short while after we had major earthworks done for out new house above the site of the trees. I was suspicious that the machinery had brought in phytophthora, and have since been careful while pruning or risking soil contamination elsewhere on the property. My questions is: can you tell by the photos what the problem is and if it was phytophthora  would the trees still be alive and fruiting after 10 years with the pathogen.