Rose Rosette Disease (RRD) is a serious condition affecting all species and cultivars of roses. It is caused by the Rose Rosette Virus (RRV), a negative-sense RNA virus transmitted by a microscopic mite. Once a rose is infected, the virus is systemic, and there is currently no known treatment or cure. The disease is almost always lethal, causing the death of an infected rose within two to five years of symptom development. Early detection and immediate removal are the only effective management strategies.
Identifying the Symptoms of Rose Rosette Disease
The most recognizable sign of RRD is the development of a dense, abnormal cluster of shoots known as “witches’ broom,” which emerges from a single point on a cane. These new shoots often exhibit an atypical, bright red or reddish-purple pigmentation that does not fade to green as the growth matures. This new growth is also frequently distorted, appearing thickened, elongated, or soft, with leaves that are small, crinkled, or deformed.
Another highly characteristic symptom is the excessive production of thorns, known as hypertrophy, especially on the newly infected canes. These thorns may be numerous, soft, and pliable when new, later hardening as the disease progresses. Symptoms usually begin on the newest growth of a single cane and then spread progressively throughout the shrub. Distorted or aborted blooms and a general decline in vigor are also common indicators.
The Cause and Spread of Rose Rosette Disease
The causative agent, Rose Rosette Virus (RRV), requires a vector for transmission between rose plants. This vector is the eriophyid mite, Phyllocoptes fructiphilus, a microscopic, wingless arachnid that feeds exclusively on roses. The mites are minute, making them invisible to the naked eye.
The primary mode of spread is the passive aerial dispersal of the mites, which are carried long distances by wind currents in a process called ballooning. Once an infected mite feeds on a healthy rose, it transmits the virus. Visible symptoms can take anywhere from a few weeks to several months to develop. The invasive Multiflora rose (Rosa multiflora) acts as a major reservoir for both the virus and the mite vector, spreading the disease into cultivated gardens.
Managing Infected Roses
If RRD is confirmed, the most effective action is the immediate and complete removal of the infected plant, a process known as roguing. This is necessary because the virus is systemic, and pruning symptomatic canes will not cure the disease. The entire rose bush, including all roots, must be dug out, as the virus can survive in living root tissue and lead to regrowth.
After removal, the infected plant material should be carefully bagged and sealed to prevent mites from escaping. Disposal must be off-site, and the material should never be composted or chipped, as the virus and mites can persist. All tools used for the removal must be disinfected with a household cleaner or bleach solution between plants to prevent mechanical transmission.
Protecting Healthy Plants
Prevention focuses on cultural practices that minimize mite transmission and remove sources of infection. Wild Multiflora rose plants should be removed within at least 100 meters of a rose garden, as they are a significant source of the virus and mites. Roses should be planted with adequate space so that canes and foliage do not touch, limiting the ability of mites to crawl between plants.
Maintaining good air circulation and avoiding the use of leaf blowers near roses can also help. Applying horticultural oil or miticides in the early spring, especially after pruning, helps control mite populations. New roses should always be quarantined and monitored for several weeks before being integrated into an existing rose bed.