Cultivated roses are facing a growing challenge from Rose Rosette Disease (RRD), a native pathogen that only in recent years has shown its potential to negatively impact landscape and garden rose varieties. RRD causes a variety of odd-looking symptoms including peculiar red growth, excessive thorniness, elongated shoots, deformed blooms, pliable canes and often leads to the eventual death of the plant. The disease was first recognized in the 1940s but was never fully characterized. Based on some similarities to other better defined pathogens it's believed to be caused by a virus or plant specialized bacterium called a phytoplasma and spread by an eriophyid mite (Phyllocoptes fructiphylus
). The disease is likely endemic to the continental U.S. and causes no visible symptoms in some native species of Rosa
, such as R. setigera
and R. palustris
Multiflora Rose (Rosa multiflora
) is particularly susceptible to RRD and it's decades long march, as an invasive plant, across much of the continental U.S. has likely been the source of inoculum and responsible for spreading the disease. Contaminated mites are easily blown from wooded or forest edges where the diseased plants may reside to nearby landscape and nursery plants. Multiflora Rose is so susceptible and the disease is so destructive that some interested in controlling the plant considered using RRD as a biological control against Multiflora Rose.
Eradication of Multiflora Rose from surrounding areas and the use of pesticides that kill the vectoring mites are currently the best defenses against this problematic pathogen. However, the long term resolution of this issue will likely rely on breeding new cultivars with disease resistant lines. Fortunately, federal, academic, and industry researchers are collaboratively working on this effort and intend to make any new developments available to growers and consumers. We will be sure to share new information and resources as they become available.
For descriptions of the symptoms and useful images check out the following disease reports:
Kansas State University
Virginia Cooperative Extension