I have a 15+ year old wild lilac (Ceanothus impressive 'victoria') located in Burien Wa. The other day I was checking the PH of the tree (Ph was 7) and noticed a large black spot with orange on two of the branches and part of the main base located about 2ft off the ground, the tree basically looks as if it has been torched. The leaves have looked normal but now some at the tip of the branches are starting to turn black, starting to curl, and some have this dark sticky goo on them. All the research I have done is pointing towards fire blight but I am confused because all the articles say that this bacteria doesn't effect lilacs over 5 years old. There was a very late heavy snow storm this year, so I was thinking that it is possible that there was damaged that we didn't notice and maybe that's how it got into the tree.
Unfortunately it's the perfect weather right now for bacteria so I am really worried cutting the infection out right now would cause more harm then good, but I also don't want to wait too long and have the infection worsen. There are two bases to this tree, however this is the main base that makes up over 70% of the tree. The other base is much smaller and behind the main base, because of the lack of sunlight is very tall and has barely any limbs. All the research on wild lilacs says the best time to do any pruning is mid-summer after the tree blooms, but all the fire blight research I have done says the best time to cut out the disease is in dead winter.
So my questions are:
1. Do you think this tree is possibly infected with the bacteria Erwinia amylovora (fire blight) . If not what do you think is possibly causing this illness and should we be concerned?
2. What do you recommend we do to help this tree and when?
Thank you so much!