Last Sunday I was at the special event of the Potomac Rose Society and the U.S. National Arboretum, called: Rose Rosette Disease: an update. It was a discussion by Dr. Mark Windham of his ongoing research conducted on Rose Rosette Disease (RRD) that he started in 2012. He was selected by the American Rose Society to lead a three-year study of RRD and how to manage and prevent the spreading of the disease by commercial growers as well as by rose lovers.

I have been introduced to RRD, and shown a plant with the disease, but for some reason I did not take it too seriously; it was bad, but controllable I thought. Needles to say, I was shocked with the information from Dr. Windham. If I am not mistaken, someone has lost 4000 rose plants. Now that was a lot of plants----so, what can we do?

We need to know how to recognize the symptoms. Be familiar how the RRD looks like.
You can easily find lots of images if you search online under 'rose rosetta virus'. However, the symptoms do not appear early on. We need a very strong magnifying glass or a microscope to recognize the virus. They are invisible without them. They look like a tiny yellow or brown banana with whiskers on one end. The virus cannot fly, but they travel with the wind. There is no rose yet that is immune to RRD. Another problem is that the symptoms are not always the same, and the symptoms do not appear quickly. And it just needs one tiny virus to take a bite of our rose bush to inject the virus into it, So if we are vigilant, when we find a suspicious growth on one branch, we could cut out the branch, and hope for the best, but if the plant is close to other plants, there is a big chance the others are infected also, but still no visible symptoms.

Dr. Windham thinks it is best to get rid of the diseased plant ASAP, carefully dig the plant out completely, not leaving any roots--it may grow back, already infected-- and put the whole plant in a black plastic bag, tie the plastic closed and put the bag in the sun, so the virus will die and then dispose the bag with the dead rose plant.

RRD is not new, but it has spread quickly when mass planting of roses become popular, around the time when Knockout roses became available. The roses are planted close together and it makes the spread easier. The virus seems to like multiflora, and it kills them, So the roses grafted on R. multiflora are considered more susceptible to RRD but no rose is immune.

Best thing that we can do at this time is learning to recognize the symptoms and there are lots of excellent articles about them with images. I just read

http://www.clemson.edu/extensi...

and

http://pubs.ext.vt.edu/content...

and I have learned a lot from them. There are many more that I have not read yet. I do not have my own photographs of an RRD afflicted rose bush, and I do not want to 'borrow' and post something copyrighted. But please familiarized yourself with how RRD afflicted rose bushes look like and help control the spreading of RRD.

Dr. Windham told us what he does when he has acquire new rose plants.
He plants them in containers and place them in a separate area, far from his other roses. After a year or two, if the roses are still healthy and he likes them, then he gives them their permanent places with the other roses.

This URL has been posted several times. I am posting it here, so more people will find it. It is a MUST READ to be able to identify RRD/RRV and its dangers if you love roses.

http://www.rosegeeks.com

1) multiflora is in the lineage of numerous roses. It is my understanding that floribunda's were originally multiflora based.
2) the mites feed on tender new growth
3) If the multiflora is buried and there are no shoots of it around for the mites to inhabit, I don't know how that would make the variety that was selected to plant more susceptible.

@Margie, R. multiflora is just one of many wild roses susceptible to RRD. So are Rosa canina, (a common European rootstock), but also the original western R.pisocarpa or woodsii where the disease was first recognized. Up to my present knowledge, any rose will develop RRD if a infected bud is grafted to it, including a rather resistant rose hybrid Mermaid (h.bracteata). Somehow these roses that show some level of resistance have some built in traits that let them go through an epidemic without major disease symtoms. Which are those traits ? Not known to my knowledge. In the original places where the disease coexists in natural equilibrium with the mite vector and the host plant, those plants that didn't develop the disease have some kind of immunity to it. (btw there' plenty of R.pisocarpa or woodsi in the N.California forests at least before these horrible extensive fires.... ).
<3) If the multiflora is buried and there are no shoots of it around for the mites to inhabit, I don't know how that would make the variety that was selected to plant more susceptible.>
It's not R.multiflora that makes it susceptible. It is if it was infected before it was grafted with a healthy scion. In otherwords if while growing rootstock there's a hidden infestation. Again the mites only feed in new tender upper tissue. These are not root mites. But once the plant is innoculated by an infected mite the full plant becomes a virus reservoir. For how long ? I couldn't find that answer yet. An infected plant is an indefinte reservoir of the virus? ( what is known in epidemiology) a healthy carrier. I don't know about this yet. Once a plant develops the disease, how much viral corpuscules have to be found inside for the plant to become a serious threat to its neighbors?
Are the mites the only vectors?. Other plant juice absorbing insects could become also occasional vectors because with their infected mouth parts go from plant to plant. (i.e common aphids). This has to be proved or discarded yet. Would I trade cuttings from someone who has had RRD in his garden? Definitely not. However if I were a research lab worker, I would ask for cuttings to be raised in quarantine conditions and figure out what made his roses survive the epidemic. Would I dig out a dead or dying rose bush. Yes, but not worry about rootlets staying in the ground. The disease is not soil borne. The virus has very short life span in the open ( hours).
However, I keep on reading and processing the available information. Our stance will change as more readily accesible knowledge becomes available. I do hope, that this happens soon! I also want to thank you and others in providing me links for reading material. This makes the processing so much easier
Arturo

hampartsum said:
Are the mites the only vectors?. Other plant juice absorbing insects could become also occasional vectors because with their infected mouth parts go from plant to plant. (i.e common aphids). This has to be proved or discarded yet.
Arturo

In addition, I think it's possible that these mites could "hitch a ride" onto gardening tools, clothes and/or wildlife (animals, birds)???
Thanks Arturo for your input - much appreciated.