Identification: Mysterious red bumps on Garry Oak

Discussion in 'Pacific Northwest Native Plants' started by Margot, Aug 10, 2015.

  1. Margot

    Margot Generous Contributor

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    When I was trimming suckers from under one of my Garry Oaks yesterday, I noticed about a dozen bright red 'galls' along a stem. They looked like miniature cranberries. Hovering nearby was a wasp or hornet. Over the next few hours, I checked the stem several times and found that there was always a wasp (or hornet) crawling over the red bumps. I did manage to open one gall and think saw a white maggot inside but I didn't have a magnifying glass to look more closely.

    Having lived in Garry Oak territory for many years now, I'm pretty familiar with jumping gall wasps and the galls they produce . . . these are definitely different . . . but what are they?
     

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  2. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    Yep, galls. Not a serious problem, they don't do any significant damage. An interesting bit of biodiversity worth preserving.
     
  3. Margot

    Margot Generous Contributor

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    Thanks for confirming that the red bumps are indeed, galls . . . any thoughts on what the involvement of the wasps (hornets) may be? I wonder if they may have caused the galls or are benefitting from them in any way. The fact that they were so persistent makes me think their presence wasn't just a coincidence.
     
  4. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    I'd guess the wasps are just licking up sugars secreted by the gall producer. But hard to say for sure.
     
  5. Margot

    Margot Generous Contributor

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    That sounds reasonable . . . I wouldn't have known that galls can produce sugars. It is always fascinating to observe what goes on in a garden; more questions than I'll ever find answers for. I appreciate you shedding some light on the galls and wasps.
     
  6. David in L A

    David in L A Active Member 10 Years

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    According to Field guide to plant galls, by Ron Russo, those are caused by flat-topped honeydew gall wasp, Disholcaspis eldoradensis, found on many kinds of white oaks.
     
  7. Margot

    Margot Generous Contributor

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    Thank you David for a great lead.

    This is getting more interesting all the time. Many more questions are coming up now, such as whether the wasps I observed were flat-topped honeydew gall wasps. All I can find on the web are pictures of the galls, not the actual wasps. Perhaps, since the galls I saw were bright red, not dark like you see in most photos, they were very recently formed. Were the wasps in the process of laying eggs or licking sugars or something else?

    There is no mention on the web of Disholcaspis eldoradensis occurring on Garry Oak trees (Quercus garryana) as far north as where I live on central Vancouver Island. Garry Fletcher in south Vancouver Island shows a great photo of similar galls on Garry Oaks that he is trying to identify -- http://www.gfletcher.ca/?paged=2 (scroll down). Perhaps these insects are new to this area. Garry says that the branches he finds the galls on usually die the following year so I hope this isn't another problem for our treasured Garry Oaks to contend with.
     
  8. David in L A

    David in L A Active Member 10 Years

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    I just noticed that Russo also shows another species, D. mellifica, which may be closer. Ruso's drawing of eldoradensis looks more like your picture than his photo does. The wasps that cause oak galls are minute. The big showy wasps are there to feed on the honeydew.
     
  9. Margot

    Margot Generous Contributor

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    Yes, the Disholcaspis mellifica galls do look more similar to mine. I regret having cut off the sucker and losing an opportunity to observe the galls longer. Then, on the other hand, if they are a new pest to this area and can be detrimental to the health of Garry Oaks, perhaps it was a good decision in the long run.

    I have heard back from Garry Fletcher who doesn't think that what he has found on his young Garry Oaks is D. eldoradensis but perhaps something called Kermes scale. Of course, we still don't know if the galls he is dealing with are even the same as mine.

    As I said before, I find this all very interesting but have to admit I'm out of my depth here.

    Margot
     
  10. Priscilla

    Priscilla New Member

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    Anyone seen these red galls lately? I’d love to find some as they can be used for tanning and dyeing — I’m involved in ancestral skills and teaching. I’d be grateful for a tip on finding some unwanted gall branches that need pruning or have been pruned. Thank you.
     
  11. Margot

    Margot Generous Contributor

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    Hello Priscilla - welcome to the forums. I wish I could help you but have not seen those galls I wrote about earlier except for that one time.
     
  12. Priscilla

    Priscilla New Member

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    Thank you! Cheers.
     
  13. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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  14. Priscilla

    Priscilla New Member

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    Thanks!
     

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