robinia mystery

Discussion in 'Woody Plants' started by emery, Sep 5, 2009.

  1. emery

    emery Renowned Contributor Maple Society 10 Years

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    Hi all,

    I have 2 Robinia pseudoacacias growing in the garden, one is the commonly grown "frisia," a well established medium sized tree, the other was crown grafted with hispida, which blew off in a bad storm, and I have let it grow out. It's a fast grower and is by all appearances the species. The 2 trees are not near each other in the garden (separated by perhaps 150 m).

    Following an extremely cold winter both trees exhibited similar problems. After leafing out normally all leaves dropped, then a second flush of leaves was sickly, often with one side browned and deformed. Many of these second leaves also dropped. They looked like nothing so much as glyphosate damaged foliage, but I use this chemical only very sparingly (in fact hadn't used it at all this year at that point), only on the paths and no where near either of these plants. On the species tree full recovery followed, but frisia's third flush was weak, there are now many dead (small) branches and twigs. On larger branches new growth has appeared closer to the main trunk. The broken branches show no signs of insect damage or staining of the wood that might indicate vascular problems.

    Anyone have an idea what may have happened, and what might be a good way to proceed? In particular I'd hate to lose frisia, a pretty and as I mentioned well established.

    I thought the problems might be linked to the cold (we saw -22C and I lost many more tender plants, particularly maples) but the information I've found has the trees as hardy to zone 4.

    Worth mentioning that there wasn't any particular caterpillar damage this year. Also, I have not seen damage to other Robinias in the area, there are many.

    Thanks,

    -E
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Timing does suggest winter damage, although you would expect these to be hardy there. A few documented cases have been reported of glyphosate appearing to damage or kill trees through their roots, see Whitcomb, Establishment and Maintenance of Landscape Plants (1987 (1991), Lacebark Inc., Stillwater). Possibly a college library over there actually has this significant work, ones here certainly do. L. Chalker-Scott seems to be dismissing this on her web site, yet if you read Whitcomb's accounts other reasons for the damage are not apparent.
     
  3. emery

    emery Renowned Contributor Maple Society 10 Years

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    I think it's safe to rule out glyphosate damage, since none was used in the vicinity and surrounding trees don't show damage. However near the Robinia pseudoacacia a late pole stage A. cappidocicum 'Rubrum', also expected to be completely hardy, died outright after initial leaf out. (A larger cappidocicum 'Aureum' nearby, better established, seemed un-phased, but cappidocicum var sinicum located elsewhere in the garden also died).

    So I tend to lean towards the cold, although why only my Robinias are effected I don't know.

    -E
     
  4. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    Any cold wet windy weather after the first leafing out? I've often seen this cause dieback on tender new shoots on Robinia, seems to be triggered by temperatures below about 11 or 12°C combined with rain and strong (usually NE) winds.
     
  5. Ron B

    Ron B Paragon of Plants 10 Years

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    If you are having a patch of sudden failure of trees close together Armillaria may be possible.
     
  6. Silver surfer

    Silver surfer Contributor 10 Years

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    emery, the RHS have written an article about Robinia pseudoacacia Frisia dying. Every where we go there are either dead trees or you can see them dying. We have lost ours, our neighbour has lost 2. As yet, they do not know what is causing them to die, and are asking members to help.

    Could it be that trees in France are now being affected?



    http://www.rhs.org.uk/advicesearch/Profile.aspx?pid=401
     
  7. emery

    emery Renowned Contributor Maple Society 10 Years

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    Silver, this sounds depressingly like what I'm seeing. In fact it sounds like an exact description, sadly. Thanks very much for the link. I only hope my tree will recover.

    I haven't noticed similar symptoms on the many frisia specimens I know. It would be a real shame if there is a wide epidemic effecting this cultivar. In particular I know of a magnificent alley of large mature specimens and the "Ecole des Roches" in Vernon sur Avre.

    Ron, definitely not Honey Fungus, no signs anywhere.

    Michael, I hope your theory is right, can't recall if we had that weather particularly, it seems we have it every year though. :) Certainly June was hot and dry, however.

    Thanks for the ideas.

    -E
     

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