I read on some site that very thick hyper-thorny stems was the death knell.

Terry,
I hesitate to offer any sort of definitive opinion as this topic always seems to derail quickly.....BUT....

I walk downtown here often to get exercise and to take mental notes of how plants are doing. Here at work we have about 20 Home Run shrubs. A block in either direction are loads of Knock Outs, and 2 blocks away is a gorgeous planting of iris, daylily, KO's, and Frau Dagmar Hastrup (I think).

I freaked out thinking that the gorgeous group had RRD earlier this summer, but I didn't call anyone or post about it. The city seems to be pretty lax & takes the easy way out of plant care; scatter some water around, mow over things, hope for the best. I figured if some unknown woman called them, the call would go ignored. Anyway, I kept an eye on the ones that looked like your photo and they appear fine now.

I wonder if the heat, lack of rain, lack of daytime humidity, use of herbicide, or some other unknown variable could be causing weird things to appear. I'd freaked out and thought I had it in my own yard a couple of times, but I'm nowhere near multiflora or any reported cases, and sure enough the growth ended up being a rogue cane or just general weirdness that later looked just fine.

You should think about how often you inspect these plants and whether weird growth began on multiple canes and plants all at once. If so, that would tend to suggest herbicide damage. Certainly it can drift 40 feet. Herbicide would tend to affect almost ALL the plants in a contiguous area. On the other hand, RRD would begin on a single cane and then spread to other canes and plants over a period of weeks. Contiguous plants are likely to be infected next, but RRD also will jump across the garden.

If the case still seems dubious, I would (1) spray the affected plants very throughly with 10% Wilt Pruf to immobilize any vector mites (2) remove affected canes at the base (3) cut the other canes back to 12" and remove any remaining foliage (4) seal the prunings in a bag immediately. I would give the same treatment to plants touching the affected plants, or at least one side of these.

This strategy of cutting back to bare stubs has allowed me to save some roses that had recent, single-cane infections of RRD while running very little risk of spreading the disease.

However, in this case, if new growth from the cane stubs looks weird, you still face an uncertainty as to herbicide vs. RRD.

I've had RRD numerous times and the picture and your description sure do look like RRD damage not herbicide damage. Unless I've had multiple canes on a single plant leaving me no room for doubt, I do as Michael suggests and cut the single cane back down to the crown. What you are hoping for is that the virus is still isolated to that one cane. I've only managed to save two plants doing this, but it's worth a shot. Here's a picture of one I couldn't save (Cl America): {{gwi:319455}}

Until one of the experts comes along, I recommend that you rip that questionable cane out down as low, as close to the crown, as you can get. Then play the waiting game--if no strange growth returns, whatever it was is gone. If it returns, then start really worrying about how serious it is--that is when you need the expert's diagnosis.

I had some strange growth just like yours--over near the neighbor's yard. I know she sometimes uses Round-up and tries to be careful, but who knows what a stray breeze might do, as in flipping a gust of Round-up right into my garden. Rather than wait around to see if the strange growth would go away (once the Round-up wore off) or if the growth would get more contorted and uglier in every way, I ripped the cane out. That was a month ago--no strange re-growth so far--so I have my fingers crossed--and am still keeping a close eye on that plant.

But if any expert has a different diagnosis, go with that. I'm no expert on this topic.

Kate

Here's another pic of 'Easy Does It'. 'Koko Loco' is also similarly affected, along with 'Hot to Trot', and others too numerous to mention. I already took out a huge 'Lilian Austin' because the canes just looked too gnarly. 'Lilian' was directly across from the neighbor's yard, but had the typical rubbery canes and ultra-thorny growth. Perhaps the mites jumped from 'Lilian' to all the others.

These symptoms have all appeared within the last 2 months. I'm hyper-vigilant and cut off any offensive canes to the ground in the hopes of saving a rose. If I take out these roses, I'll have a huge void in the middle of the hillside.

That's a good illustration of RRD from maryl just above. Notice there are just TOO MANY new shoots coming in that limited area. Also, the dense rubbery thorns are a very common RRD symptom, but not universal. The RRD shoots I recently found on 'Clair Matin' were nearly thornless. And, maryl's new shoots have small, twisted leaves. On many varieties, RRD produces oversized leaves that are crumpled in a way different from normal new leaves of that variety. Often RRD leaves are a darker, more intense purple-red than normal new growth. But on some varieties, new RRD leaves are green or green with red veins.

I'd say the OP's one picture isn't enough to definitely say whether it is RRD or herbicide. It doesn't show the pattern of shoot emergence or degree of thorniness, etc..

Sorry, I cross-posted with terryjean and missed her second photo. I'd say that's RRD. I would follow the cutting-back procedure suggested in my first post, and dig any rose that comes back with bad growth. If you do it that way, you can be fairly confident that you aren't letting the plant strew infected mites around while you wait for systemic infection to reveal itself with certainty. I'm afraid I let that happen in my garden when RRD first appeared in one plant this spring.

Darn. Well, 'Easy Does It' has it so bad it can't be salvaged. I have some pretty rare Cliff Orent roses that are in close proximity, so I'm going to march out and spade it. Rats. Thanks, Michael G.

Since Professor I. E. Tzanetakis, University of Arkansas, Fayetteville, AR, U.S.A. is apparently doing funded research on rose rosette virus, I suggest that you contact him to see if he is willing to test one of your "suspect/possible/probable" plants.

My Ebb Tide looked exactly like your pics. I removed it and will let the ground lie fallow for a year or two. Rather be safe than sorry.