I'm pretty sure those are galls.

Where did you get the tidbit about fasciation? I guess it makes sense. Genetic engineering. Maybe we can figure out how to make an oak tree that would grow dining tables.

The most common roses on which galls are reported are R. elganteria. Most often, the galls are reported from northern states and Canada. In the past two years, there have been photos on here (GW) of galls on roses other than eglanteria, but always from northern gardens.

The galls I had on eglanteria that I mentioned here about a month ago went to the state ag people who confirmed them as galls, but were unable to identify which species of wasp caused them. I tried to get them excited about a southern record of a gall on roses and they finally confirmed that none had been reported from TN before.

On my R. eglanteria's as well as those I've seen from farther north, the hyperthorniness was confined to the gall part, not to the stem above or below it. It didn't seem to be xylem or phloem transmitted.
(I do have photos of my galls, but our transfer mechanism isn't working this month.)
And there is a gall out there that is even thornier than the one in Cass's photos.
About fasciation, at least some fasciation is phytoplasma caused. (The phrase "Asters Yellows' was used for a disease that more recently has been shown, in some plants to be phytoplasma caused.)Lots of papers about Cockscomb, Celosia deal with this, and there's a recent paper (2007) about phytoplasmas in weeds in Iraq.
As for the oak dining tables, burled woods sell for great prices so you might be onto something for the future. Mr rose galls weren't woody, though, under the thorny parts, almost pith like cells surrounded the larvae.

Michael, thanks for that.

The book is called The Field Guide to Plant Galls of California and Other Western States by the UC Berkeley Press. It is readable and full of excellent illustrations and up to date information. There's a short chapter on rose galls of the Western states. There are so many rose galls that I've actually photographed galls that aren't in the book. 17 bux. The author is a 30-year student of plant galls and has named dozens of them. Insect-induced plant galls are the poster child for the co-evolution of plant and parasitic insect communities. Good stuff.

Here is a link that might be useful: Field Guide to Plant Galls

There's a recent paper about phytoplasma in roses that links it to proliferation (under a different name) and other disorders, if I recall correctly.

Ann, there was a spiny rose gall posted here this season from Louisiana.

How in the heck do the wasp larvae do this? Do they secrete altered versions of plant RNA?

The phytoplasma in roses papers are mostly from eastern Europe where they've had a heck of a problem with total losses of Greenhouse rose production in some greenhouses.
One of the main authors is Kaminska. There are at least four papers. One of the more recent mentions RRD and says it's not the same.
Some of the symptoms are very similar.
But theirs appears to be leafhopper transmitted.

I've been slogging through plant virus papers lately. Really depressing reading. And the different known plant viruses and how they are replicated.
Then we come to RRD which doesn't fit any of them, although there are other diseases with similarities to RRD.
The paper by Ahn, Kim, Gergerich, Jensen and Anderson, 1996, in the bibliography linked below outlines the proposed new virus family.
The hows and whys of the plant replication of the diseases is only beginning to be understood for some of the crop diseases that have major economic impact. Blackcurrent Associated Reversion Disease ends up being a complex of diseases. The wheat and corn eriophyic mite spread diseases are getting research money and they will probably be the first big breakthrough.

And thanks to Cass for the reference. I should have it via ILL by this weekend.

Here is a link that might be useful: RRD bibliography

Ann, rose galls are common on all California species roses, including the non-native, naturalized species - - that includes the Eglantine. I think I'll check what had that stem gall at the Arnold Arboretum. One was R. nutkana.

I'll read the book, and then ask questions.
The only thing I forgot to add above was the plant pathologist's comment that the larvae would have to go to a specialist for identification of the species.
To me that implies exterior morphology of the gall isn't definitive.
We just don't see that many galls. We do see the eriophyid mite's much smaller galls on poison ivy and occassionally on oak leaves.
I do know that there's not a whole lot of R. eglanteria in this part of the country. How did the wasp find mine (which had been here about four years, three of them wasp-free? Alternative hosts?