Acer Palmatum Disease?

Hi! Any ideas of what is this darkening in the bark of my Acer Palmatum?? Please I’m very concerned, any ideas would be helpful. I’ve read Michael Hagedorn’s but I’m not sure to if it’s Pseudomonas syringae.

Thank you!

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@SamuelNavarro, it looks like sun burn to me. Have you thinned it recently or had lots of sunshine?


It is definitely a fungal infection and a bad one.

Pseudomonas is a very likely candidate.

I manage to save my Acers first by pruning hard until there was no sign of the fungus in the inner layers,

removing them from current soil and putting them to completely inorganic soil with a bit of

sphagnum moss second (this has to be a thin layer in an extremely ventilated pot), and finally

spraying systemic fungicide to prevent it from infecting the rest of the plant.

I lost only 1 in 9 palmatums and the specific one was young and weak to begin with.

Best of luck with this nightmare.

P.S Do not leave the tree exposed to full sun after you do the above


Hi @dylan.burt Thank you for your response. I really hope is a sunburn. You’re right, it had lots of sunshine for the past month.

Hi @Silva_Aeternam Thank you for the response. I hope is a sunburn as dylan sugested. If not, I’ll proceed by pruning it hard.

I would not suggest waiting as I am 100% sure that it is not a sunburn.

It will keep spreading to the rest of the trunk and kill your tree rather quickly…

It seems radical, but I am afraid is the only way (at least that I know of, most people advise discarding the tree completely).

Pseudomonas is a bacteria FYI, not fungal.

Sorry, my mistake mixed it up with phytophthora there.

Thanks for the correction