Confronting Rose Rosette Disease
If you’ve talked roses with friends in your rose society or on Facebook, you’ve likely heard the name rose rosette disease, or RRD. While it’s been around for a few years, it’s now starting to show up in more and more community & home gardens. And it’s a killer . . .
First, what is it?
It’s a disease that is carried by a very specific spider mite called Phyllocoptes fructiphilus. An infected mite drifts on the wind, comes into your garden, lands on the tops of your rose, and then injects the disease into the rose when it starts to feed. Or a non-infected mite lands on a rose that already has it, picks it up, and then is blown by the wind to another rose, which it proceeds to infect. It’s the perfect survival technique during blustery Spring weather. . .
Beware of the witches broom
You know you’ve got it when your roses start to develop twisted purplish growth that has foliage in the shape of a “witches broom” like the below images. (It looks a lot like Roundup damage.)
Where did it come from?
It is particularly lethal to the wild rose species R. multiflora – and in fact has been mentioned as a potential biological control method for it. R. multiflora spreads like crazy, so much so that in much of the eastern United States it’s classified as a noxious weed.
In their attempt to control it, some government officials even facilitated the spread of RRD by purposely infecting large rambling stands of multiflora. They claim there was no scientific proof RRD infected ornamental roses, the kind we all grow in our gardens.
Well, guess what? Nature does find a way. RRD does affect ornamental roses – although some more than others. Currently, there are no known roses that are completely resistant to RRD.
How can you avoid it?
Everything starts with R. multiflora, so check with the rose society in your area about wild stands of that species. R. multiflora is a rambler and so throws off long canes that bloom in spring with smaller white flowers that have five or so petals each. That’s the easiest time to spot it.
When it’s not in bloom, checking the foliage helps. It’s shiny green, and the leaves are elongated. It’s usually thornless, which makes it really stand out. If you have it, you can dig it up and get rid of it. That’s probably your first step.
What can you do if you find it?
If RRD does happen to infect one of your garden roses, there is no known cure – but there are still steps you can take. The first one is understanding how it spreads in a rose. The mites land on the top of a rose cane, where the new tender foliage is. They inject RRD into that part of the rose, and from there it slowly travels down through the main cane to the base and then up the other canes. The important word here is slowly.
Typically, the symptoms on the infected cane (the witches broom) often show up before the rest of the plant is infected. So the minute you see the witches broom, follow that cane to the base of the plant and cut it off at the base. Then gently put it in a garbage bag and get rid of it so you don’t accidentally shake any mites onto another rose. Eventually the cut-off cane is replaced by a new one, and it’s as if nothing ever happened.
However, if the disease appears to have spread into another section of the rose, you have no choice but to dig the entire rose up and get rid of it via the plastic garbage bag method. Also, it’s not a good idea to plant again in this bush’s soil until you’re sure that all remaining roots from the diseased roses have been removed.
I’ve met other gardeners who have lost a few bushes, but once they understood how to deal with it & spread their success, the local incidents were reduced.
So does this mean you should simply stop growing roses?
Of course not! RRD is scary when you first get it, but by knowing how to spot it & deal with it, you can reduce it to a manageable part of normal garden maintenance. Just keep an eye out for it, and act quickly.
