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dark-rimmed grey/white lesions or plaques on omurayama japanese maple

There are dark-rimmed grey/white patches on my recently gifted Omurayama Japanese maple. Is this due to disease, or simply sun damage? There is the uncommon hole on leaves rimmed with the same grey-white color, as well.

Benjamin Van Biber
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  • I have a Korean Frost Maple with the same stuff on the branches. I assumed it was normal until reading this post. – Evil Elf Oct 15 '13 at 13:22
  • It may be normal- I'm new to these maples; but I will look into the Korean Frost maple, and see if it is the same. Thanks for mentioning it! – Benjamin Van Biber Oct 15 '13 at 17:45

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I am going to put an educated guess out that this is sun damage. Why? Notice that all of the dead spots are on the tops of the most exposed branches, but not the undersides, and not the protected branches. With a fungus attack, you should expect the worst areas to be where the exposure is lowest, and the air circulation is poorest.

I have seen this type of damage become infected, though, however, the damage was more extensive, and the tree was not growing fast enough to heal properly. With a proper leaf canopy for protection, I don't think this will happen. Eventually, as the tree grows, the young bark will begin to mature, and develop a light grey-brown cork layer. This may first appear as spots similar to the ones on your plant, but these are normal on a trunk/branch of increasing diameter.

J. Musser
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