Summer gold leaves brown spots

Discussion in 'Maples' started by Stuart McKenna, Jul 10, 2021.

  1. Stuart McKenna

    Stuart McKenna Member

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    I seem to be getting a lot of brown spots on the leaves of my summer gold. Anyone any idea what could be causing this. Could it be too much water as we have had a lot of rain ?
     

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  2. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Hi Stuart, IMO it is from all the rain and then some sun hitting the leaves. But, have you looked underneath for aphids ? This weather is bringing a lot of them out once again.

    D
     
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  3. Stuart McKenna

    Stuart McKenna Member

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    Thanks D I did check for aphids and it's definitely not that, I guess it's this weird summer we are having
     
  4. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Glad you have ruled that out Stuart. I agree this Summer weather appears to be strange, but tbh it's like I remember as a child, so perhaps not so unusual. Our trees have got to adapt yet again it seems.

    D
     
  5. Stuart McKenna

    Stuart McKenna Member

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    Funnily I always seem to remember summers being hot and dry as a child, must be selective memory
     
  6. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Ahhh, depends on how far you go back, Lol.

    D
     
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  7. Jaybee63

    Jaybee63 Rising Contributor Maple Society

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    The long hot summer of 76, now that’s a year never to be forgotten.
     
  8. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    No rain spots that year!!
     
  9. ChrisUk

    ChrisUk Member

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    Hi Stuart, I've seen the same things on my Summer Gold in the past few years. It's planted in full sun, and quite exposed.
    These spots are - like Acerholic said - probably cause by rain drops and then hot sun afterwards.
    It's a bit unsightly, but nothing bad for the tree, I think.

    We could see these on the side of the tree exposed to the sun. The other side and the inner leaves were all ok.
     
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  10. D97x7

    D97x7 Rising Contributor 10 Years

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    Plenty of ladybirds though.
     
  11. 0soyoung

    0soyoung Well-Known Member

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    I note from the pix that it appears the only leaves with spots are on top or the leaves with the most exposure. Leaves below (in the background of the photos) don't appear to have spots.

    Hence I think it is possibly the early stages of sun-burn OR
    that droplets of something like an herbicide was accidentally splashed onto the tree, not plain ole water.
     
  12. Stuart McKenna

    Stuart McKenna Member

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    Thanks, definitely not herbicides but could be sun although we haven't had a lot lately
     
  13. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    That is good to know N.
     
  14. D97x7

    D97x7 Rising Contributor 10 Years

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    It was the year of the plague of them.
     
  15. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Ahh of course I remember now.
     
  16. maf

    maf Contributor Maple Society 10 Years

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    I agree with the comments about strong sun hitting water drops with a magnifying glass effect. The yellow leaved cultivars seem particularly susceptible to this, noticed some big brown spots on shirasawanum 'Aureum' leaves exposed to strong afternoon sun the other day. I think it is most likely to happen when you get short sharp showers followed by intense 1pm sun when the leaves have partially drained but leaving a few isolated large water drops to act as magnifiers.

    One interesting thing to note is that when I get these spots on atropurpureum leaved plants (usually seedlings) the spots are very light brown or what might be called tan, rather than the dark brown on the yellow leaved cultivars.

    (There may also be bacterial infections involved, but I have always thought these were secondary infections gaining access to the sun magnified burn spots.)
     
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  17. Stuart McKenna

    Stuart McKenna Member

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    This seems very plausible with the weather we've been having, great explanation thanks a lot
     
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  18. ChrisUk

    ChrisUk Member

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    Stuart, I looked earlier at my Summer Gold and I've got some spots (see photo), same as yours. And they've started appearing during the past month where there has been lots of sun/showers/sun transitions.

    Maf's explanation is great
     

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  19. emery

    emery Renowned Contributor Maple Society 10 Years

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    I remembered drops acting as magnifying glass and burning leaves is a myth, but wasn't sure and so looked it up. Here's what Dr. Chalker-Scott says on the issue:

    https://s3.wp.wsu.edu/uploads/sites/403/2015/03/leaf-scorch.pdf

    My 'Summer Gold' was planted in-ground last year, and has lots of little brown spots, which I put down to a poorly established root system. We've had a lot of rain and not too much burning sun; this plant hasn't been manually watered this year.

    Cheers guys, -E
     
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  20. maf

    maf Contributor Maple Society 10 Years

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    I don't always 100% agree with Dr. Chalker-Scott, although often I do. In this case I believe she is talking about general leaf scorch and leaf dieback, not specifically round spots on leaves. From the article linked above:
    and:
    This is clearly different from the round spots on leaves pictured in this thread, which show no marginal or tip necrosis.

    Maybe the magnifying glass effect of raindrops is a myth, maybe not? However, I can't think of a better explanation for spotting that only affects leaves exposed to both rain drops and strong sun.
     
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  21. emery

    emery Renowned Contributor Maple Society 10 Years

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    Hi Maf,
    I'm the same. In this case, the search turned up a number of other references including this one

    Can water burn plant leaves?

    which I think I'd seen before. (I confess I only glanced at the article I posted, having I though read it before). As you say, that's an explanation, but the preponderance of evidence doesn't seem to support the idea AFAICT.

    cheers, -E
     
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  22. maf

    maf Contributor Maple Society 10 Years

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    That's quite funny because I was actually reading that exact same same article when you posted! (and a couple of others about the same/similar studies, I've been considering this subject and trying to find research of which there is not a great deal). The interesting section I found was:
    Now, the interesting part I thought was "the light would be brought to a focus underneath the water droplet, and inside the body of the leaf" which proves that the water drops cause extra irradiation from UV etc of the interior leaf tissue. I am sure that they used a fairly hardy species for these tests and not a sensitive yellow leaved cultivar of Japanese maple. We all know that the yellow leaved JM cultivars are more susceptible to all types of leaf burn due to some physiological characteristic that is associated with the yellow colouration. Could it be possible that on a still and very humid day, such as recent weather here in the UK, circumstances conspire such that a midday raindrop from an isolated shower would persist on a leaf without evaporating for long enough for the focussed sunlight to cause tissue damage in a very sensitive cultivar? I believe it could... but as always I am willing to change my opinion if I see incontrovertible evidence (which in this case would be the experiments replicated on the leaves of Acer shirasawanum 'Aureum', A. palmatum 'Orange Dream' or similar).
     
  23. 0soyoung

    0soyoung Well-Known Member

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    Raindrops could also contain spores, bacteria, and viruses. Wet spores 'germinate' (if that is the right term). The infection occurs pretty much coincident with the water spot.

    My anecdotal evidence is that I have a crabapple and had a unidentified vine that I grow/grew in pots. When I watered and splashed the foliage, I always got brown spots where the water tended to hang on the leaves. If I sprayed a peroxide solution immediately after having sprinkled the leaves, there were no brown spots.


    Not meaning to be nasty, I think your statement belies your unwillingness to challenge your long held beliefs and see if they stand up to the test.

    The yellow coloration comes from xanthophyll, compounds that divert photoenergy away from PSII. Instead of the energy being used to disassociate water into oxygen and protons, it becomes heat. Many alpine conifer species turn yellow in winter as the xanthophyll protects the granula from being chemically damaged by sunlight in the deep cold of the winters they endure. But there are yellow leaved conifer varieties used for landscape purposes. Similar to Orange Dream, these will be green in shade but yellow in bright sun and as the leaf gets older, the yellow foliage tends to be sun-damaged or 'sun burned' as some call it. It is a common phenomenon involving some common physiology. Is it because of the excess heat generated by diverting the photoenergy away from PSII that kills cells?
     
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  24. maf

    maf Contributor Maple Society 10 Years

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    That is an interesting post, particularly the last paragraph and last sentence. IMO it provides a possible explanation of why water droplets exposed to sun would cause damage to the areas of leaf where the light was lensed on yellow leaved cultivars high in xanthophyll but not have the same effect on green leaved cultivars with normal xanthophyll levels.

    I had also considered the possibility of infection by damp loving spores/fungi/bacteria, but as this issue is not found in the lower leaves that stay damp for much longer I had discounted this as the primary cause of damage in this instance, but accept that secondary infection is possible with the pathogens taking advantage of damaged cells to gain entry to the leaf tissue.

    My statement about what evidence I would need to see in order to change my opinion was admittedly a bit over the top, lol, but I can assure you that I am perfectly willing to adapt my beliefs as the reality unfolds.

    As it stands I still believe there is some connection between the lensing of radiation by water drops on yellow leaved JM's and spotted damage to the exposed leaves. Even the quoted studies say that water drops do not "usually" cause leaf damage, and I agree they do not, but when dealing with yellow leaved cultivars is this not an unusual situation? These cultivars are only in existence because they have ornamental value and in nature they would likely be out-competed and result in an evolutionary dead end.
     
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  25. emery

    emery Renowned Contributor Maple Society 10 Years

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    I guess I'd be surprised if the scientists doing the study used very photo-insensitive leaves, at best that would be a poor experiment. If I want to capture radiation, or it's effects, I'd use a detector that was as sensitive as possible without being saturated. Still I don't doubt that green leaved plants were used at the least, and we all know that yellow burns more easily that green.

    The key seems to by evaporation vs. time to build up heat from lensing.

    But what I'd like to see, before changing my mind, is any serious experiment that supports leaf burning from lensing. Do we have anything that passes beyond the purely anecdotal? (This way we can all camp in our corners and shout: "I'm right", lol).
     
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