Star Magnolia disease?

Discussion in 'Magnoliaceae' started by mekanic, May 5, 2006.

  1. mekanic

    mekanic Member

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    Location:
    Hamiloton, Ontario
    We have a star magnolia tree located on the north side of our house. During the past two years it developed a black soot-like coating all over the trunks and branches. In addition there are greyish to tan coloured lumps attached to the branches that are crumbly if you push them or try to remove them with a stick. Last year there were many bees attracted to the tree. The soot looks just like the black exhaust deposits you would get from a poorly tuned automobile exhaust pipe. Can anyone help me diagnose this problem and how to treat it? Thanks
     
  2. Junglekeeper

    Junglekeeper Contributor 10 Years

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    Location:
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    The tree may be infested with scale. The sticky honeydew is a byproduct which attracts other insects and the black soot is fungal growth on it. A review of threads containing [search]scale and tree[/search] may prove useful.
     
  3. Richcr44

    Richcr44 Member

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    Hi

    I have the same exact problem with my Star Magnolia and do not know how to treat it.
    How did you treat your problem?
    Thank you
    Rich
     
  4. MAH

    MAH Member

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    I sympathize with your problem. Here in Toronto, I have a mature saucer magnolia, maybe 25-30 feet tall, infected with the same insect. Diagnosing is easy --- if you search the web for "magnolia scale", you'll easily find lots of information and photos. This is a "soft scale" , Neolecanium cornuparvum, better known as Magnolia Scale.

    I've spent a lot of time looking for solutions, and I've had a professional tree-care company treating it in the Sping and Fall for about 10 years or more. The trouble is, we're having an "outbreak", and magnolia scale hasn't been easy to control in the past few years.

    In my experience, the spray treatments (horticultural/dormant oil, insecticidal soap) which I've paid an arborist to apply to the tree, aren't all that effective. (And I've read that chemical pesticides, even if there are any that are still legal to use, would kill off the insect's predators too, and so would just make things worse.)
    I've seen recommendations for "manual" treatments --- i.e. rubbing/brushing off the insects --- but if you have a 25-30-foot tree, that's hardly feasible.

    I'm reaching my wit's end with this problem. This is the 3rd summer that my back-yard is un-usable --- I can't enjoy the garden, which I've created with some care as a sanctuary from the stresses of life. The digested tree-sap which is excreted by the scale insect drizzles down on the whole backyard (a city yard, 25-feet square), so that everything -- flowers, plants, furniture --- is covered with sticky sap. And there's a black mould/fungus that grows on the sap, and lots of insects are also attracted to it as a food source. So you see why the back-yard is un-usable.

    I've been told by an arborist that lots has been done to try to control this insect, with limited success, and that many tree companies are just giving up.

    So I'm starting to seriously consider taking down this beautiful tree. It's become more a problem (another source of stress), than a joy. And the cost really adds up --- $120 each for 5-6 spray-treatments per year. If anyone knows a solution that works for a 30-foot tree, I'd welcome hearing about it.
     
  5. Ceurdge

    Ceurdge New Member

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    Hi MAH,

    Thank you for the insightful description and sharing your experience.
    I am in Toronto and have the same situation as you with two 25-35 feet magnolia trees.
    In my case the infestation must have started last year and is really significant this year.
    As your post was in July 2010 I'm wondering if now in July 2015 you've found a long term solution.

    Thanks in Advance,
    Ceurdge
     
  6. MAH

    MAH Member

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    Hi Ceurdge,

    What a surprise to get a note on this old thread!

    So you have 2 big magnolias, with scale all over them! I sympathize, but I think there IS a solution. (Btw, mine are saucer magnolias, with the large pink-and-ivory flowers.)

    Well, I've managed to control those little bug(ger)s -- but they do keep coming back. Some years there aren't many, some years there's an "explosion" of them. 2010 was particularly bad and it took a while to get rid of them, but in the past few years it's been okay.

    What eventually worked was persistence, and money. I wasn't willing to chop down the tree, so I paid a tree-care company to do what they thought was best, and that was to spray the tree, twice in the spring and twice in the fall, with either horticultural oil or insecticidal soap. If it's a year without too many insects, I can get away with maybe spraying only in the spring -- but I learned, through painful experience, that I couldn't "skip a year" of spraying -- even though I may hardly see any of the insects, I still had to pay for at least one or two sprayings per year, to keep the scale under control.

    So that has worked. But it does cost. The 2 sprays this past spring were $300, plus tax. (and I think they may be giving me a slight discount because I've been using them so often). And because I'm seeing a few bugs on the tree now, they'll likely suggest I spray in the fall as well, for another $300. I've been using Ontario Tree Experts for years, and I'm happy with them. I basically do whatever they suggest, including occasional fertilizing and pruning.

    I think the mistake I made, that contributed to that awful situation in 2010, was to try to economize and cut back on the spraying (or even skip a year) if I couldn't see many scale insects. That just didn't work. Particularly in 2010 when there happened to be an extreme peak in the scale population here --- nobody could foresee that, and then it took a while to get rid of them. You really have to be consistent with regular spraying, to keep the population way down.

    Sometimes I wonder if it's worth it, but then each spring those thousands of huge pink flowers.....

    Good luck with your trees! I'd be interested to hear what you decide and how you make out.
     

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