Rose Rosette Disease
Rose Rosette Disease (RRD) is a terrible rose disease that we’ve been hearing about for years, especially from the Dallas area. Unfortunately, we are starting to see more cases in Williamson County. Rose Rosette has been around since the early 1940’s, but the problem seems to be growing in recent years as cultivated roses are used in more and more landscapes. In 2011, Rose Rosette was diagnosed as a virus and researchers have recently confirmed it is spread by the eriophid mite Phyllocoptes fructiphilus.
Eriophyid mites are microscopic mites (3 to 4 times smaller than a spider mite) that can be transmitted by wind or landscape tools from infected plants to healthy plants where the mites feed and introduce the virus. The mites tend to hide in rose buds, on open flowers or sepals, or at the base of shoots, leaf axils, and leaf scars during the winter. The virus appears on new foliage in the spring.
Typical symptoms of RRD include elongation and thickening of the shoots/stems; red leaf mottling; leaf distortion; excess thorns that are flexible; yellowing and stunting of plants; witches’ brooms; flower distortion; branch/shoot dieback; and reduced winter hardiness. The “witches’ broom” is a very common symptom of RRD, and it’s a brush-like cluster of shoots and branches that originates from the same point. This growth is also called a “rosette,” which is where the disease gets its name. Witches’ brooms spread randomly across the plant, and the flowers fail to open or look distorted.
Researchers all over the United States are working to identify treatments and rose varieties that are resistant to RRD. Right now, early detection and removal of infected plants is the best way to reduce the impact and spread of the disease. Infected plants should be removed and disposed of immediately, including its roots. Place in a sealed bag and dispose of the plant off-site to keep the mites from dispersing to another plant. Wait one to two months after removing an infected plant before planting a new, healthy plant. Miticides like bifenthrin, carbaryl, or endosulfan can be used to control the spread of the mites.
