Many of Madison’s residents may look around their gardens or city property and wonder why some of the ‘Knock Out’ roses look funny. They may notice that the stems and leaves have a bunched, distorted appearance. There may also be many, many more thorns, giving it a bristle brush look. They may note that the new-growth, bright burgundy leaves are not turning green and may appear to be stunted or much thinner.
Blooms may look smaller or discolored, and may fall off without opening. Eventually they notice that the plant is dying. If this is the case, the roses they are seeing may have contracted Rose Rosette Disease (RRD).
According to Liz Cuneo, President of the Madison Beautification Board, there is still no cure for Rose Rosette Disease. It is caused by a tiny mite called an eriophyid. It feeds on the roses, and then travels on the wind to other roses, thus spreading the disease. As the disease is systemic, once the rose is infected, it is virtually impossible to treat. This is what is happening to the roses in Madison and all of North Alabama.
Once the rose has been diagnosed with the disease, the only solution is removal. It is hoped that removal, which in effect thins out the roses, will slow down or stop the spread of the disease by making it harder for the mites to travel. It is important to remember that if you remove a diseased plant, you remove it completely, to include the roots. It should be bagged and sealed before placing by the curb for trash pick-up.
It is believed that the rapid spread of the disease here in North Alabama is due to the large numbers of the ‘Knock Out’ which have been planted. While the ‘Knock Out’ rose is disease resistant, no plant is disease proof. As in any landscape, diversity is best.
As RRD affects all roses, not just the ‘Knock Out’, it is recommended that a few precautions be taken when planting new roses. Make sure not to plant a new ‘Knock Out’ where one has been removed. You must wait before replanting in the same place. You can, however, plant a different type of plant where a ‘Knock Out’ has been removed as this disease only affects roses. It is recommended that you plant your new ‘Knock Out’ on six foot centers. Roses should not touch. One of the problems the Beautification Board has noticed is that roses planted too close together, producing the beautiful massed effect we see around town, is a bridge for the disease-carrying mites to travel from plant to plant.
Cuneo suggests that if residents believe their roses have the disease or want more information, they should contact Ken Creel, Madison County Extension Agent at 256-532-1578 or 256-382-1554. Residents may also find more information and pictures in a comprehensive article from the University of Virginia at http://pubs.ext.vt.edu/450/450-620/450-620.html .