Japanese Maple - dead branch & sawdust at base

Discussion in 'Maples' started by jf_webster, Aug 9, 2006.

  1. jf_webster

    jf_webster Member

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    Webster Groves, MO
    I've lost a major branch originating from the base of my Japanese Maple over the last few weeks (all leaves turned brown). The rest of the tree looks fine. I was looking at the dying branch and noticed what appeared to be fine sawdust at the base and possibly some very small holes in that same area (occurs just on dying branch). The bark on this branch is loose at the base. See attachment.

    Any thoughts on whether this apparent infestation caused the branch to die or if this is more of a secondary issue? The tree was probably under-watered during this timeframe. I'm trying to decide how to treat the rest of the tree and maybe several others I have in the yard depending on the root cause.
     

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  2. Laurie

    Laurie Active Member Maple Society 10 Years

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    Interesting how you write about "the root cause." Verticillium wilt, caused by fungi that enter the tree through the roots, is an important disease of maples, but there is not enough information, at least to me, in these photographs to determine if this tree may have this problem. Check out this thread: http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=15882. My first impression regarding the 'sawdust' is that it is secondary to whatever doomed that particular branch. In this area we have both termites, which eat the wood, and carpenter ants, which nest in the wood. When you remove the branch at the base, if you think that it is dead that far down, check out the cross-section for signs of verticillium wilt. Disinfect the pruning shears afterwards. Feel free to add some more photographs of the operation, including one of the wood, when the peeling bark is pulled back. We may not know what is going on, but we would like to learn with you.
     
  3. jf_webster

    jf_webster Member

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    Thanks-
    I'll continue to investigate and see if I can provide more details. I think I'll cut off the branch and see if the cross-section provides any insight. At least the branch was towards the back so the tree still looks great (so far)...
     
  4. Scion Swapper

    Scion Swapper Active Member

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    My initial guess, as I've seen it here fairly prevelently over the last year, is Verticillium wilt. Here in the Mid Atlantic states, we had a rather severe drought last summer/fall, which stressed many japanese maples. This year we saw the aftermath, as many even established trees lost major portions of their canopys to Verticillium wilt. A local parent tree to a named witches broom, 'Carl's Corner Broom', was also destroyed during this time (entire broom destroyed with some parent tree remaining). Some stock plants that we have at the nursery, which were located in areas without the best irrigation schedule, were also lost. Perhaps your tree was stressed as a result of last years environment and didn't make it out of its slump.BTW, the heat waves seen this year could defoliate any tree planted within the last two years, especially if a rigorous irrigation schedule has not been followed.

    Best of luck,

    Brian
     
  5. Galt

    Galt Active Member

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    A little sawdust is usually an indication of entry by a borer which will subsequently girdle the branch or trunk causing death. Look for a small hole. Usually a borer does not enter or attack a particular area of the tree unless it is already compromised. While vert might have compromised the tree it has little to do with sawdust.

    The one issue might be that if the branch is already dead and the sawdust is just appearing it probably died before it was attacked by whatever insect cuased the sawdust. A borer or vert might have killed it previously and now another chewing critter is feasting on the dead wood. Just hard to know what happens unless you can clear the time line up for yourself.
     
  6. jf_webster

    jf_webster Member

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    I decided to remove the limb this weekened. I've attached a number of photos. It looks to me like it is infested with the Asian ambrosia beetle. From what I've read this insect can introduce fungus. I was able to cut below the entry point of the insects (they had bored about 1 foot up from the base) and I see no other entry points on the other limbs.

    From the reading I've done it sounds like I should spray the base of my other maples with some form of permethrin insecticides. Apparently systemic insecticides have not proven effective for control. Any other recommendations or conclusions welcome.
     

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  7. Laurie

    Laurie Active Member Maple Society 10 Years

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    It seems that a number of ambrosia beetles, so-called because they bring fungus into the tree with them for the larvae to feed on, may attack maples: Asian ambrosia beetle; black stem borer; black twig borer; European shot-hole borer; shot-hole borer. The latter was mentioned in Vertrees and Gregory. Japanese Maples 3rd Ed. (Timber Press 2001). It appears from some of the articles online that some of these beetles and borers have made their way across the United States. Thank-you so much for sharing these photographs with us. Good work on the identification of the problem, but it does sound as if "it looks ... like" the Asian ambrosia beetle, but that it is not a definite identification. The cross-section of this branch looks just like Verticillium wilt, The fungus introduced by the Asian ambrosia beetle can act just the same way as Verticillium in blocking transport through the tree, and a cross-section of a damaged trunk can look similar. However, the discoloration in this branch is opposite the beetle tunnels. If this branch has been dead since winter, and it was caused by the introduced fungus - various articles list Fusarium and Ceratocystis as pathogenic fungi - then this is the second year of this beetle infestation. If there was definitely neither sawdust nor frass until recently, then it is likely the first season, and Verticillium was responsible for weakening the tree, thus making it more susceptible to attack. If you can get a sample of this to your local extension office, then perhaps they can determine, which fungus caused the death of this branch, and which of the ambrosia beetles is definitely responsible. It may be wise to take a sample in as this may be the first case reported in a Japanese maple in Missouri. I have only been able to find reports of Asian ambrosia beetle attacks on black walnut in Missouri.

    If you do not take a sample in, the control for both Verticillium and for further infestation by the Asian ambrosia beetle is to keep the maples as healthy as possible. That means feed them lightly now, water them regularly, but don’t allow them to sit in wet soil, and keep other pests and diseases away. Frankly, I would remove the ivy or other ground cover from under the tree, where both fungi and pests can be harbored. Since you may be dealing with the most aggressive beetle of the bunch, which will attack both sick and healthy trees, it just may be a good idea to monitor the beetle activity by hanging a non-homemade ethanol trap as suggested by some authors. It sounds as though it is too late in the season to use pyrethroids because they needs to be used when the beetles are active, otherwise it will have no effect on the beetles in the trunk. However, this is not at all clear to me. I would definitely burn the wood soon as advised in some of these articles. Please keep us updated on the diagnosis and control.


    http://extension.oregonstate.edu/wasco/horticulture/Pesticide Management/ambrosiabeetle.php
    http://apps.caes.uga.edu/news/getstory.cfm?storyid=173
    http://ceris.purdue.edu/napis/pests/aab/AABfactsheet.pdf
    [FONT=&quot][FONT=&quot]http://www.uaex.edu/Other_Areas/publications/PDF/FSA-7064.pdf[/FONT][/FONT]
    http://oregonstate.edu/Dept/nurspest/Xylosandrusgermanus.htm
    www.aces.edu/timelyinfo/PlantPathology/2006/May/pp607.pdf
    http://oregonstate.edu/Dept/nurspest/xyleborus_dispar.htm
    http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7421.html
     
  8. jf_webster

    jf_webster Member

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    Thanks for the suggestions. I'll see if anyone at the local Botanical Garden is interested in confirming what infested the tree (and if this is news in this region). I didn't realize there was more than one type of ambrosia beetle. It looks like the holes run parallel to the wood grain which probably eliminates some of them.

    Just to clarify - The tree looked healthy this spring and early summer. I wasn't monitoring the base so I don't know when the sawdust started. This branch went from looking healthy to dead in about 3 weeks. I don't know whether the branch was stressed. Some articles I've read mentioned that this beetle is known to attack perfectly healthy trees. I'll be sure to focus more on feeding/watering in the future.

    I found a number of articles that found that the traps used for the Japanese beetle can be effective. It may give me a good indication when these bugs are active.

    I'll post an update if there are any developments.
     

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