We can't call that an auto imune disorder. Not at all.
In the auto imune disorder in animals, the imune system tries to actively destroy its own organisme by mistaking it with an agressor. Maybe that can lead to the same result (ultimately death), but the process and causes are very different.
Trees aren't designed like the animals and their protecting system/strategy is completly different: They don't know how to heal/repair, they just close the old/dammaged part and continues to grow around/over it. But what we see here is a backfire of the system. It's the same event with a massive attack of insects borer, on the spruce like here in the very recent past for exemple. If there's only an handfull of attack points, no worry. The tree isolates something like 1" around the hole/galery, closes the gates and paths mecanically, loads the cells with "awful" chemicals to contain the agressors. The life continues around the blockage. But if there are hundreds or even thousands of borers, the tree has to close the same amount of areas, to the point of having no longer enough functional tissues. All the above starves from water and all the under starves from nutriments, to death. Unlike the borers with a very small damaged area (for each ones), the fungi and bacteria have the potential of a wide spread progression inside the tree (even if they aren't a killer by themselves). So the tree isolates a massive area, keeping about nothing, or so few, to function properly. Basicaly, he kills himself yes, but due to a colateral dammage.
