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Old Lilac with fire blight #745736

Asked April 22, 2021, 4:04 PM EDT

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! 

Snohomish County Washington

Expert Response

Here are some more pictures



On Thu, Apr 22, 2021, 1:04 PM Ask Extension <<personal data hidden>> wrote:

Dear Kaylie,

Thank you for using Ask Extension. A request for support has been created and a representative will follow-up with you as soon as possible. You can view this question's progress online.

YOUR QUESTION #0015667:

Old Lilac with fire blight

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! 

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The Question Asker Replied April 22, 2021, 4:11 PM EDT

Your Ceanothus is not actually a lilac--that's just the common name.  Syringa vulgaris the name of the shrub that is most commonly known as Lilac.  We don't see a lot of fireblight in the PNW, although we do see a similar bacterial disease, Pseudomonas syringae.  Neither of these are known to affect Ceanothus species.  It's obvious that you have a canker or cankers on your bush.  The lifespan of Ceanothus is around 10 years, and can be considerably less in poorly drained soil and if given too much summer water.  Your old bush may have lived out its life.

Let's try to get to the bottom of this problem. The injuries on the tree--are they on one side of the tree--south or west facing?  When did you last prune it?

Alice Slusher Replied April 22, 2021, 4:20 PM EDT

The injuries are just on the South side. The shorter limb is about 6-12  inches below the other. 

The last time we pruned was last summer and it was just a light trim off the very top and some off the sides. Nothing close to where the cankers are.

The Question Asker Replied April 22, 2021, 7:13 PM EDT

The injuries are just on the South side. The shorter limb is about 6-12  inches below the other. 

The last time we pruned was last summer and it was just a light trim off the very top and some off the sides. Nothing close to where the cankers are.

The Question Asker Replied April 22, 2021, 7:18 PM EDT

I think it is most likely winter injury. I don't think this is an infectious process.  This generally happens on the south side of a tree.  The sun will shine on the dark bark and warm it up--the juices warm up and start flowing.  And then it gets very cold at night, and the plant can't adjust to the temp change.  This is an injury we see fairly frequently in early to mid spring with our sunny days and nights that can still get very cold.   Read more about it here. https://pnwhandbooks.org/plantdisease/pathogen-articles/nonpathogenic-phenomena/winter-injury-landscape-plants-pacific

With luck, the plant will heal itself. Once our weather settles down, chances are your bush will start to put out healthy leaves.  My guess is the "burnt" looking ones also  suffered cold damage.  Here's an excerpt from the article above:

What to Do for Winter-injured Plants

Don’t do anything until late spring when new growth begins on the live wood and does not begin on the dead wood. Before doing anything, check to be sure the crown is alive. Then prune to remove dead wood.

  • Prune properly. Do not leave stubs. Prune back to live, green, heathy wood. Prune to a bud, stem, or trunk. Give a suffering plant a chance to become healthy again. Prune out only dead and severely damaged wood.
Alice Slusher Replied April 22, 2021, 8:33 PM EDT

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