(Possibly related to Naadhira's issue)
NE PDX santa rosa plum. 4 years old (ish). Gets good sun, in clay soil on top of a slope. Some of the leaves in the middle of the branches are shrivelling up and dying. They aren't discolored or misshapen, just shriveled and dessicated with some green remaining. The leaves on the tips seem ok, and if i look closely at a newer branch that's been affected, there is some discoloration near where the leaves used to be, like that part of the branch is also dying . The branches most affected tend to be the lower ones, and moreso inside the canopy than at the edge.
Last year it got plum pocket and I sprayed with copper soap just before budburst.
Today I pruned out what I could, and I have been careful about removing the dead leaves. A couple plum pockets have emerged, but better than last year and I can't tell if there is a correlation.
I also attempted a graft on it this year. Didn't take... could it still be a disease vector if it didnt take?
My current hunches are that it could be a) some kind of bacteria, b) related to the plum pocket, c) the cost of using a spray , or d) a spreading of the verticillium wilt that infected a nearby rosebud. I fantasize that its just getting rid of leaves it cant use, but that seems too hopeful.
I am hugely frustrated as this is the first year it set a real amount of fruit. Any ideas? How worried should I be?
Thanks in advance for your thoughts,
Dawn
Sometimes rootstocks don't behave in ways they are expected to and could produce somewhat of a "leggy" kind of look. If there is any chance the tree was sold to you grafted on 'citation' semi-dwarfing rootstock and if so then I'm pretty sure I'm right. The citation patent never was adequately tested long enough for peaches, then all of a sudden farmers found peaches, although dwarfed, turned out leggy. So peach is no longer farmed on citation. I have tried many plums and plum hybrids as multiple grafts on the same citation, and I even used to have a 'frost' peach on another citation. With the peach I started noting the leggy effect in about the 3rd year and it was the most confusing thing to me at the time and I finally did altogether remove it.
My newest plum on my multi-citation tree is 'Owen T' which according to the resemblence to 'santa rosa' is probably Rosa's daughter, and it is the only leggy plum of all everything currently grafted there, and I honestly don't know what to do either. 
When I grew Santa Rosa, my plum tree had a lot of problems. It's a great plum tree for dry areas of California, and the plums taste great when grown there. However, I don't live there.
I switched to other types of plum trees: Hollywood, Shiro, Beauty, Methley, and others unnamed. Italian plum and Damson. They don't have problems, I get tons of plums and no problems. These plums grow well in PNW.
John S
PDX OR