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Disease/disorder on Japanese Acer

What is causing the stems/branches of my Coral Bark Acer (Acer palmatum Eddisbury) to turn black?

When I first purchased this tree back in 2010 the spot it was growing in became waterlogged in 2011 and it was very poorly (or at least I thought that was what the problem was).  I removed it from that particular spot and nursed it back to health after pruning it as much as I dared.  It seemed to recover and came on leaps and bounds.  I planted it in a new spot that never becomes wet/sodden in winter back in 2013 and it has been happy ever since.  Until now that is!

From the information I can find it might be verticillium wilt or phytophthora.  Any opinions or thoughts?

I am resigned to the fact that it should go if it is either of the above and will need to find an alternative tree for that spot.  Will I get away with planting something that is resistant or should I leave the area unplanted.  

Thanks in advance for any help and suggestions. 






  • BobTheGardenerBobTheGardener Posts: 11,391

    Pseudomonas syringae is a strong possibility.  A bacterial infection not at all helped by cold and wet (a slight tiny wee small problem for those of us in the UK then!)  I have had several Japanese acers affected but pruning well below the damaged area seems to help.  Unfortunately acers don't really like being pruned either..

    There aren't really any chemical treatments left that we're allowed to use, but copper sulphate can still probably be found, although you wouldn't dream of using it as a fungicide/bactericide of course..

    A trowel in the hand is worth a thousand lost under a bush.
  • WintersongWintersong Posts: 2,436

    I had to remove the an Acer palmatum recently because black stems alerted me to problems. It had already lost one significant branching the previous year due to unidentified dieback. This time I knew something significant was going on and pruned a section of dead stem to confirm virmiculum wilt. The stems show discoloured circles or black patches 

    ofc it's still only a guess as research suggests it could be a pseudo form but with a fully grown acer and many plant choices in my garden that are susceptible, it had to go image

    good luck with yours 

  • Lion SLion S Posts: 263

    I don't know if it's available in the UK, but in the Netherlands there's a product called "Mucoter" which has been developed to control soil-borne fungal pathogens. Eco-friendly, as it's a highly concentrated herbal mix.

  • AngieRAngieR Posts: 347

    Apologies for not responding to your replies sooner.  I am not usually so rude image 

    Aym280 - on closer inspection today it seems to be that what ever is causing this is affecting most of the main stems/branches and I think pruning back to undamaged wood would mean leaving a single spindly stem nearer the base.  Thank you for bringing air layering to my attention.  I will have a look at you tube.

    Bob the gardener - I had never heard of this condition before so thanks for providing the link.  I've read it and it could perhaps be the cause.  Since I've already pruned this once gorgeous tree and is now rather oddly shaped I think more pruning would leave it looking even worse and as you say they don't like being pruned and it is certainly not wise to prune now.  Time for a replacement.

    Wintersong - I will cut into the branches to investigate once I've got it out the ground.   I think you did the wise thing and I will do the same before it affects anything else.  I've an extremely mature dwarf Acer that would break my heart if I lost it.  It has fond memories.

    Lion S - I have tried googling your suggestion but am coming up a blank for anything here in the UK.  Thanks anyway.

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