I had heard of Rose Rosette disease, but never read about it or even looked at pictures, so I didn't know until today what the symptoms were, and now I think I have 2 Knockouts with it.

I noticed last year this section on the rose growing really fast and dark red. I have attached pics. They are in a group of 6 total shrubs, but these are the only 2 with symptoms.

What should I do? Should I just destroy those 2 that have symptoms, or the whole group in that bed? Can I replant in the same soil?

I can't tell from your picture. Does the new growth also have wild thorns and "twisted" leaves? If not it may just be normal enthusiastic growth - especially if it did this last year and turned green later.
If you are sure it is diseased you need to remove it - roots and all - as soon as possible.

It never turned green, it stayed red. It does have some distorted small leaves.

What about the other plants without symptoms? Should I destroy them too?

And the soil, can I plant more roses there?

I can certainly understand why what you see on your Knockout rose might look like it has rose rosette disease. My guess is that it does not.

As Porkpal said: For many roses it is normal for new growth to have a purplish hue. In my garden Europeana and Double Delight both have it. It is also normal for new growth to be a little distorted, especially if the rose is growing quickly. The roses with RR appear to be covered with distorted leaves. On your rose there is a lot of normal-looking fresh new foliage. Also, it looks to me like the Knockout foliage in the photos of RR disease is more red than purple. Not sure that's an important distinction.


If you get to a point in the summer where your roses are taking a break but the distortion and discoloration persist, I think I would have it checked out by someone who actually knows something about RR.

Yes, it is just one or two canes on each plant, the rest are normal. Would it be the whole plant that was affected?

It never turns green, like the rest of the plant. New growth starts red but eventually turns green, but these canes do not, and they are quite a bit faster growing that the remainder of the plant.

If this is so prevalent in multi-flora, I wonder why nurseries would use multi-flora root stock to graft their roses?

Palatine, for example, uses multiflora rootstock. They grow their multiflora plants from seeds precisely because rootstock grown from seeds is virus-free. Rootstock propagated vegetatively as must be done with, say Dr Huey, is only as clean as the plant from which it was taken.

I tried to explain a little earlier: I think the reason multiflora rose is considered a vector for the virus is primarily because it is one of the few roses that satisfies all three of these epidemiological criteria:
1) it gets the disease
2) it thrives in the wild, growing on for a while after being infected, and
3) it was widely planted in the wild.

Most cultivated roses, I think, will get RR but most do not satisfy the last two conditions. I don't have any reason to believe that a healthy multiflora plant near a garden poses any more risk than a healthy version of nearly any other rose cultivar. Except, perhaps, a cherokee rose which is not bothered by the mites that spread the virus. (That said, I think there are a lot of better choices for a zone 6 rose garden than a white multiflora rose.)

Keep an eye on the cane that is growing quickly - the one with the deformed leaves. My personal guess is that the fact that it is growing quickly explains both the purplish color and the deformation of the leaves. If, when it stops growing, the deformation and the coloration persist, photograph it again. Start another thread here. And start preparing yourself to destroy some roses.

I think one of the most tell-tale signs is the difference in the thorns. Infected roses have really gnarly thorns that are much different from the healthy plant.

I sent some photos to Ioannis Tzanetakis who is in the department of plant pathology at the Univ of Arkansas, that is where they actually found the virus that causes rose rosette. This is the answer I got from him.

"The symptoms I see do not resemble rose rosette disease. I do not see any excessive thorniness on the plants and symptoms are not systemic. Have you checked for powdery mildew? The other alternative would be a phytoplasma."

Thank goodness. I have not seen any powdery mildew on the roses. Anybody know what phytoplasma is?

No clue - but good news!

Well, I found this info

Phytoplasma are intracellular bacteria exclusive to plant and insect species and have been identified as the causal agent for over 1000 different plant diseases.

Good news, yes.

Phytoplasma is another pathological agent (like bacteria to humans) - suggesting Tzanetakis believes there is a pathology associated with malformed leaves. This I know even less about.

Last year I discovered 10 roses with Rose Rosette disease on my property. This year so far, two more have it. There are wild multiflora growing in the fields near me, and I suspect the mite that carries the disease blew from those plants to mine. Wichita has many many commericial plantings that are totally infested with RRD, and business owners have been reluctant to totally redo their landscape, so the disease continues to spread. Our botanical gardens and the county extension display gardens both have found it in their plantings. We first tried just removing the infected canes, but now the recommendation is to remove the entire plant from the ground, bag up the entire thing, send it to the landfill and never plant a rose in that space again.
I have only had to totally remove 2 plants so far. One was an Austin, the other was an old favorite, Auguste Renoir. I have knockouts with the disease, Souvenir de la mal maison has it, Austins, scarlet meidiland, and Jacob's Robe. Maybe the minis won't get it?
Two people in our rose society have lost their entire collections of roses to RRD. At our sale today, customers were asking for roses that are resistant to it.....sadly, we know of none.
And no cure, so far.
On all but the two plants, I seem to have stopped the progression of the disease by removing the infected canes. Time will tell if it returns to those plants. It is possible, I admit, that if I had totally removed the first plant that first showed the disease, that no other plant would have been afflicted.
Mary, I would cut out those canes that show the red fast growth. Cut them way back the the base of the plant, and then clean your pruners with alcohol. See if new growth is reddish and thick, or if it is green like the rest of the plant. I hate to disagree with an expert....but that sure looks like the RRD when it first showed up on my plants.
If I see more here, I'll post close up photos.

That's very sad.

I'd like to believe that if I saw RRD on a plant in my garden I would dig it up immediately, bag it, and get it out of here. I understand, though, that it would be difficult to do so - especially if it were rare and/or if it were one that I had worked of for years to get established. It's hard for me to understand how one part of a plant could harbor the virus but another part be free from it. I guess I thought that's not the way it worked.

My understanding is that the virus itself does not survive in the soil. It can, however, survive in bits of root left in the soil. And Zuzu tells a tale of a rose disappearing for a few years and reappearing. So it might be good to wait a few years before re-planting roses there.

All this vegetative propagation: it keep plants standing still while pests and diseases make evolutionary advancements.It seems to be the perfect way to breed and propagate ever more virulent plant pathogens. Makes me worry for the future of all agricultural pursuits.

Although I am not sure what the case at hand has to do with phytoplasmas, I thought I might post a link to this paper about phytoplasmas: http://www.plantgem.unina.it/A...

It's a little technical, and a little sketchy. But it it makes some interesting points:
- Phytoplasmas are related to bacteria, have no cell walls, and, in fact possess a rather limited subset of the biochemical machinery that had, until their discovery, been assumed to be needed by all living organisms.
- This makes them utterly dependent upon their hosts. They cannot, for example, be cultured in a petri dish. And this is one of the reasons they have only recently been studied.
- They tend to travel lightly, change surface morphology fluidly, and live off the land, making it very difficult for the immune systems of their hosts hunt them down and destroy them.
- They have been implicated in a lot of plant diseases: the symptoms of which are frequently either "witches broom" formations or leaf yellowing. The consequences are generally destructive in cultivated plants, but there is an exception in poinsettias.
- Interestingly, phytoplasmas are sensitive to tetracycline.
- There is evidence to suggest that certain other microorganisms might aid plants in recovering from phytoplasma diseases.

...

One thing that occurred to me in reading this was that in the case of phytoplasmas it takes the carrier insect three weeks from the moment of ingestion to the moment it is infectious and can transmit the disease. If one had the technology and were inclined to do so, it might hypothetically be possible to clean the garden of insects every two weeks, meaning that each new infected insect would have to fly in from somewhere else. Not sure I'd be inclined to try to do this because if pesticides were used it could devastate the populations of insect predators, making the garden completely dependent on the gardener for insect control.

Another idea is to spray plants with lemon or eucalyptus oil or some other agent that repels insects.

Cindi can you see infected roses growing in the wild? Or is it possible for multiflora rose to carry the virus with no outward symptoms?

The multifloras around here look asymptomatic. That's what is so confusing. My neighbor didn't want me removing the multiflora that grows on the bank of the creek that separates our properties. The roots hold up the bank, so I understand,.
We have ancient hedgerows with hedgeapple, cedar, russian olive and multiflora. They were planted at least every mile here. probably in the 1930s.
Steve, thank you for the link and explanations. Our local rose society has cussed and discussed the topic. A few members spend their retirement traveling to great gardens, and they've gone on hort tours with experts who are working on the RRD issue. We've talked to Bayer reps ( I used to be a Bayer rep also) and reps from Weeks along with researchers at the college level.
The work Steve cited makes the most sense to me.
We have a large colony of wild bees on the property--the beekeeper who moved them from the wall of our house to a box out in the yard estimated it at 50,000 bees. I can't/won't use insecticides, even if it means I give up roses.
There are various shrubs on the property who have witches' broom here and there, and I cut them off when they show. I wonder if it's the same phytoplasma?
I'm interested in the tetracycline aspect. Might do some googling on that after dark tonight.

(At the risk of repeating myself) I'm with you on not using insecticide, Cindi.

I'm not sure exactly where bees live around here. The rocky landscape, I think, might have some great cave-like locations for bee hives. When the nepeta and salvia are in full bloom, the garden is positively buzzing with activity. Seems to me that is a precious and under-appreciated resource.

Another precious resource in my garden is lizards. There are at least two different species, and they are ubiquitous. As I sat in the hammock the other day I think I was able to see five in plain view at once. Each must eat dozens or maybe hundreds of tiny insects per day. And if I could see five, there must have been two or three times that just out of sight. Insecticide would kill those guys long before it got all the insects. So the first time I sprayed insecticide, I would risk ruining the garden for at least a year, maybe more. Then not only could I not grow roses, I couldn't grow anything else, either.

I only use insecticide on ant hills when they first appear. Or if paperwasps are building a nest in my eves or in my grill. Otherwise, I leave things alone. But I can't handle ants! Give me any other kind of creepy crawling other than ants or crickets, but I don't go outta my way to kill crickets. Yesterday when DH & I were cleaning the garage, my one dog, Sebastian, kept chasing around the bees. He loves to eat them. I kept yelling at him to stop it.. leave the bees alone!! They're too precious!!

I only do yellow jackets. I don't mind paper wasps unless they build a nest somewhere that's a real problem, like an electrical outlet or the grill.

Given what yellow jackets can do to a hive, I'm sure the bees don't mind me doing away with them. There's a large wild hive two doors down from me and my yard is full of honey bees.

I also end up with a LOT of ladybugs and ladybug larva. Those are great for aphids.

I wish there was a good way to get rid of rose curculio. I understand there isn't much that's affective on them and they are so destructive to the rose buds.