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Thursday, February 18, 2010

Hydrangea wilt updated


Last September, I posted an entry about a situation with our hydrangeas where entire stems were dying mysteriously. I thought I had identified the problem as mushroom root rot after reading the Alabama Extension Agency's fact sheet on hydrangea diseases. Well, it turns out, I was wrong! I am a blogger (and librarian for heaven's sake), not a professional botanist, but it pains me to disseminate false information. I'm here to correct the situation!

Earlier in the week, our local Master Gardener's association held their monthly meeting and featured a wonderful speaker, Lisa Barnett, from the American Hydrangea Society. She had the same problem with her hydrangeas and a colleague sent a sample to an expert at the University of Georgia who identified the culprit as a borer - the Black Twig borer, Xylosandrus compactus (a cousin of Ambrosia beetle, Xylosandrus
crassiusculus). Lisa thinks the droughts of previous years contributed to the problem and weakened the shrubs, making them vulnerable to attack.

If you suspect this in your garden, look at the hydrangea stems closely. You will see a tiny hole along the stem where the insect has entered the plant and sawdust-like substance on the ground. To help eradicate the problem, cut the affected canes completely to the ground and burn them. Do not throw them on your compost pile! If a shrub seems to be completely infected, destroy the entire plant. The borer also attacks other shrubs and trees with similar sized branches.

Let's hope this cold winter will kill off some of these nasty buggers!

I plan to monitor our hydrangeas carefully this year and I urge you to do the same.

Text and photos by Phillip Oliver, Dirt Therapy

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11 comments:

  1. Sound advice for those in your corner of the globe. I hope you can deal with the problem effectively now, your hydrangeas look magnificent in previous posts.

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  2. This is good to know. I hope not to see such a thing here. I have lots of hydrangeas.

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  3. Phillip, that is a shame that you may have to destroy them. But at least you know and have been able to warn others.

    Hydrangeas bring such great color & texture to a garden.

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  4. I agree with Lisa...I have not seen this problem in Illinois (as of yet!!) and hope I will not. I have added many hydrangeas to my property over the past few years and would hate to lose them. Good luck with yours!
    P.S. You have an interesting blog - I am new to blogging and realize I have much to learn... :)

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  5. Who knew?! I wonder if this is what killed my limelight. I had assumed it was some sort of fungus/rot.

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  6. Yikes! I don't grow the hydrangeas that you do...and boy are yours beauties~but I'll pass this info onto friends. Thanks Phillip, gail

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  7. Fortunately, this hasn't hit hydrangeas in MI yet, but it's good to be aware of. Yet another reason I love reading blogs from around the country! :)

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  8. Oh, man, that is the pits. Glad you figured out what it was. I'll keep watch on my hydrangeas too.~~Dee

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  9. thanks for comments

    http://www.rdrop.com/~paul/hulse.html

    this is the site that i found that explained how to do the rose cuttings - like i said it's the wrong time of the year - the rose has no leaves, but i still hope some of them make it. Good Luck!

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  10. Philip, thanks for the tips on the Hydrangeas.
    BTW, your hydrangeas look great

    Aanee
    Irish Florist

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  11. I just discovered this borer in my own garden. I am new at gardening, but planted Hydrangea's this spring - one of my favorites. My husband & I purchased a hundred yr old farmhouse with an acre of property, so there was already a well established Hydrangea there, and now they both have what appears to be the "black twig borer" you described. Were you able to get rid of it? Do you have anymore tips? Thank you!

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