what is this?

sluiceJune 12, 2012

Saw a Juniperus osteosperma a few days ago with some of these things growing on it. Any ideas? Thanks.

J. osteosperma

J. osteosperma

J. osteosperma

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jimbobfeeny(5a IN)

Looks like a witch's broom - That's where most funky conifer selections originate. Try grafting it onto a rootstock and see what it turns into!

    Bookmark   June 12, 2012 at 9:07PM
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kbguess(z5 IA)

mistletoe ?


    Bookmark   June 12, 2012 at 10:24PM
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treebarb Z5 Denver


Mistletoe was my first thought, too. I tried finding pics, but they don't look quite like that. The growth seems too different to be a broom. I hope it's not mistletoe.


    Bookmark   June 13, 2012 at 9:03AM
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Hmm, maybe it is a broom, or some sort of disease.

Here are a couple of pics of juniper mistletoe from a J. monosperma in New Mexico, which looks like Phoradendron juniperinum.

Phoradendron juniperinum (?)

Phoradendron juniperinum (?)

I had thought about trying to root that small rosette, and even brought one home with me.

    Bookmark   June 13, 2012 at 10:51AM
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greenhaven(SW MI z6)

Well of COURSE you brought it home, lol! It will be interesting to see how that comes out.

    Bookmark   June 13, 2012 at 2:02PM
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I've enjoyed reading some of the threads in this forum, as I'm a fan of conifers.

I was curious about the cute little growth on the juniper, so I went to Google. Here's what I found:

It appears to be a gall, the home of the larvae of juniper tip midge (Oligotrophus betheli).

You can look for mining and exit holes "found at the junction between living and dead tissue or at the base of the swollen portion". This is from the Pacific Northwest Insect Management Handbook: http://insects.ippc.orst.edu/pnw/insects?16LAND10.dat

This midge lays its eggs in Juniperus occidentalis, J. scopulorum, J. virginiana, but is especially common on J. osteosperma in Colorado and Utah according to the book 'Forest Entomology' by William Ciesla.

Although from western N America, the juniper tip midge is also an expat in Serbia; it was first identified there in 2007 on J. virginiana.

The number of rosettes in the gall is between 5 and 20. A photo of galls is on p.59 in www.aspensite.org/FTP/Colorado_insects_Feed_Trees.pDf

And finally, people who study galls are called cecidologists!

BTW Sluice, nice pics. Your third photo looks like that of a beautiful christmas tree ornament.

    Bookmark   June 13, 2012 at 7:12PM
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Whoops! Didn't mean to send this twice.

    Bookmark   June 13, 2012 at 7:14PM
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Thanks IshCountryGal!

Tomorrow I'll inspect it for mining and exit holes.

    Bookmark   June 14, 2012 at 12:10AM
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So here is the gall, there were 10 small rosettes.

After pulling apart each rosette, I noticed the juniper tip midge larvae were still in the gall.

Oligotrophus betheli larva in Juniperus osteosperma gall rosette

A close up of the juniper tip midge larva

    Bookmark   June 14, 2012 at 10:06AM
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greenhaven(SW MI z6)

What amazing photos! It makes me so happy when folks are curious enough to really explore. What a great learning experience, thanks for sharing!

    Bookmark   June 14, 2012 at 10:30AM
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Thanks greenhaven!

To complete the story, this is Glenwood Springs, CO where the gall was found. That's the Roaring Fork river coming down the valley, from Mt. Sopris in the background.
A nice mix of J. osteosperma, J. scopulorum, P. menziesii and P. edulis along this canyon.

    Bookmark   June 14, 2012 at 11:47AM
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Really nice work sluice! That's a mighty little midge to provoke that response from its host.

I envy you the beautiful blue sky in the last photo. We're in the midst of "June gloom" here in the pacific NW.


    Bookmark   June 15, 2012 at 2:39AM
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Yep, Juniper gall midge. I remember seeing them on J. osteosperma in the White Mts in California. This species seems particularly prone to them, though I've read they occur on some other junipers too.


    Bookmark   June 15, 2012 at 4:44PM
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