Over the past couple of weeks, I have found Rose Rosette Disease on three of my roses. Never heard of this, you say? Most people haven't, so don't feel bad.
Rose Rosette Disease (abbreviated RRD) is a virus, or virus-like, disease of roses that is transmitted by an almost microscopic wingless mite and it is almost always fatal. It is important that rose growers be aware of the symptoms, and be prepared to take action should the disease affect one of their roses.
I first found RRD symptoms on "Miriam's Pink Powderpuff", a hybrid perpetual rose that I am very fond of.
Abnormal new growth, hugely hyper-thorny, with stunted flower bud.
Deformed flower and an unbelievably, abnormally thorny stem.
Normal new growth on "Miriam's Pink Powderpuff" should look like this.
RRD causes new growth to be unusually large, abnormally thorny, grotesquely concentrated and contorted. The red color can also be an indicator, but don't use this as an absolute sign because many roses normally have red new growth. Symptoms are highly variable, so it is important to recognize what normal growth looks like on various types of roses.
RRD on a cane of 'Baron Girod de l'Ain'
RRD can cause all the growth buds at an infected node to break and grow at once. The arrows point to places where there are three sprouts from each node. This contributes to the concentrated nature of the Witch's Broom growth.
This tiny new sprout on an infected cane clearly shows that there are three new stems coming from one growth point ... not a normal situation for 'Baron Girod de l'Ain'.
This is what healthy new growth on the Baron should look like. The new leaves are bronze red, and they quickly turn green. The stems are thorny, but not hyper-thorny and menacing like the canes with RRD.
This morning while I was working in the Rose Field, I saw this in my row of modern shrub roses.
Witch's Broom growth on 'Gentle Persuasion'
As I pulled aside the weeds, the full extent of the contorted nature of this cane was obvious.
RRD on this rose has caused abnormally concentrated, thorny growth and deformed flower buds.
Normal new growth on 'Gentle Persuasion' is much more mannerly ...
... and the buds are a lovely butter yellow.
There is no cure for RRD. If the disease is noticed early, while there are symptoms on only one cane of the rose, you may be able to save the plant if you remove the entire affected cane ... I have saved one rose this way. The only reason I even tried to save it is because it was a very rare rambler, and I'm one of the only people on the East Coast who grows it. It has been a year since I removed the abnormal cane, and I have seen no sign of RRD on that rose yet.
Most of the time, the disease has already spread to other areas before you notice it, and it will show up again as soon as new growth starts. This is what happened to "Miriam's Pink Powerpuff". I noticed abnormal growth on her early this spring, and I removed that cane. Now that the disease has returned, I know that it is probably throughout the plant, and I have removed the whole thing. "Baron Girod de l'Ain' and 'Gentle Persuasion' will leave as soon as this heat wave breaks.
The absolute best reference I know to educate yourself about Rose Rosette Disease is an e-book written by Ann Peck. Ann is one of the country's leading authorities on RRD, and she has been studying and tracking the disease since the 1990s. In the introduction of her book, Ann says, "I hope this book will educate rose growers so they can recognize RRD early, take the proper actions to deal with it and continue to grow roses."
While RRD is a concern to rose growers, I will never let this prevent me from growing roses. To put this in perspective ... I have more than 800 roses in my garden and in pots waiting to be planted, and I have had RRD in my garden a total of only six times so far. From talking to other rose growers, conditions this year seem to be favorable for RRD transmission. I doubt I have seen the last of it this year ... though I sure hope I have.
RRD may mean the death of the infected rose, but it should not prevent you from growing and enjoying roses. Get educated ... read Ann's book.
To read Ann's book, click HERE.