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treeweaver

Expert needed! JM bonsai fungus HELP!!

treeweaver
10 years ago

Hi everyone, long time lurker here, and I have finally been driven to post...

I received a Japanese Maple (Deshojo) bonsai one month ago as a gift. I have many plants and a couple bonsais, but this is my first Maple. I live in Southern IL (zone 6a), and our weather has been pretty warm and humid the past couple weeks.

Last night I noticed, what I am assuming is powdery mildew showing up on the leaves (this is my first spring here in So. IL, and I was over misting with the humidity). I spent most of the night and morning researching what to do. Unfortunately, there is a lot of information/conflicting information on the web about what not to use, but no details on what exactly is an acceptable non-systemic fungicide spray for JMs.

I decided to use Daconil Ready To Use Spray this morning, since it looked like it was going to be a cool and overcast day. Well, the "spray" setting and the "stream" setting are virtually the same, and I ended up dousing the tree in two quick squirts. I even ended up getting the trunk in places, so I tried to dab off as much of the excess as I could. And to bring more misfortune to my story the sun ended up coming out and warming up the day. Luckily, the tree was in the shade, and I got it indoors not long after it started heating up. - I'll know next time to dilute it with my own mist bottle.

So now I have what could be a beautiful Japanese Maple with a fungus problem, maybe other problems, and some leaf burn. Here are my questions and concerns:

-The plant was nearly defoliated with the exception of 4 medium sized leaves when I received it. (Apparently, this helps with the shipping?) Could this mid-spring, almost-full defoliation give me more grief later on come fall with the added stress I just caused by burning some/many of the leaves with the Daconil?

-Obviously, the tree has been weakened for multiple reasons, so when would it be safe to sprinkle it with a pinch of fertilizer to help bring it back given it was just doused with Daconil?

-What is a safe red leafed JM fungicide spray to use?

-When will it be safe to let this little guy back outdoors in its place where it receives morning/evening sun?

-I realized that this tree probably shouldn't have green leaves yet, but it does have some. Could this be caused by another problem?

-What do I need to do to nurse my tree back to health?


I realized I've done more harm than good. I should have just tried to wash off the leaves before spraying it with fungicide, and gave it a little more sun to cook off the rest. Next year, if there is a next year, I'll be giving it a nice systemic soak at the beginning of the spring as a preventative measure.

Here are images of the healthy leaf sprouts (bright red), the burgundy leaves (burnt by the Daconil), green leaves sick looking leaves (notice the remaining white powdery specs):

Any advice is much appreciated, thanks!

Comments (3)

  • cearbhaill (zone 6b Eastern Kentucky)
    10 years ago
    last modified: 9 years ago

    Step away from the tree.
    Honestly, that's the best advice I can give.
    Set it outside where it can get a bit of morning light and leave it alone.
    You identified over-misting as the problem, so stopping that would have been enough. Best advice for anything is to correct the cultural issues and wait to see improvement.

  • treeweaver
    Original Author
    10 years ago
    last modified: 9 years ago

    Thanks for the reply, cearbhaill. I know that I just need to stay away and let it do its thing. That was my problem all along. I was just so fascinated by it, and love it so much that I was giving it too much attention. Like I said, this is my first spring here and first maple, and I just was not used to the high humidity. Thanks for the advice.

  • gardengal48 (PNW Z8/9)
    10 years ago
    last modified: 9 years ago

    Japanese maple foliage is extremely sensitive and spraying it with anything other than plain water can create a phytotoxic reaction.

    FWIW, with the vast majority of woody plants - like your little bonsai - powdery mildew is purely a cosmetic issue and nothing that will seriously harm the tree. I agree 100% with cearbhaill - just let it be. Misting is completely unnecessary. Water as required at the base, thoroughly wetting the pot and potting medium.

    The tree should releaf. JM's can lose foliage for a variety of reasons and still produce a new flush of foliage. I'd keep it out of direct sun at all times until it has responded to a more normal growth patterns. And generally I would advise against any fertilizer but containerized or bonsai'd trees DO require supplemental fertilization. I'd wait until the plant has releafed and then use either a single application of slow release (like Osmocote) or a dilute liquid every 2-3 weeks.

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