Rose Rosette Disease (RRD) is a serious, untreatable condition that specifically affects roses (Rosa species), causing significant deformities and plant death. The disease is characterized by striking visual changes, including excessive, soft thorns, abnormal reddish new growth that fails to turn green, and dense, clustered shoots known as “witches’ brooms.” As RRD has become a widespread concern for gardeners, a common question arises regarding its potential to affect humans or animals. This article examines the nature of the disease and the necessary precautions when handling infected plants.
Is Rose Rosette Disease a Human Health Risk?
Rose Rosette Disease poses no known threat to the health of humans, pets, or livestock. The causative agent is the Rose Rosette Virus (RRV), a plant-specific pathogen with a highly restricted host range. Plant viruses, including RRV, are biologically distinct from viruses that infect mammals. RRV requires specific cellular machinery found only in roses (Rosa spp.) and cannot replicate or cause illness in human or animal cells. This biological barrier means that even direct contact with an infected plant or the microscopic vector cannot transmit the disease to people or animals.
How the Disease Spreads Among Roses
The Rose Rosette Virus (RRV) is spread primarily by a tiny insect known as the eriophyid mite, Phyllocoptes fructiphilus. This mite is microscopic, measuring less than 1/200th of an inch, and acquires RRV when it feeds on the sap of an infected rose. Mites can only crawl short distances, but they are easily carried long distances by air currents, drifting onto healthy roses nearby. They also hitch rides on gardening tools, clothing, and animals, which can inadvertently carry the virus.
Once the infectious mite feeds on a healthy rose’s tender new growth, it transmits the virus. After a latency period of several weeks to months, the infected rose begins to show characteristic symptoms. These include the “witches’ broom,” a dense cluster of malformed shoots, striking red coloration on new stems that does not fade to green, and a proliferation of soft thorns. Early identification and removal of these symptomatic plants is the only way to slow the spread of RRV.
Protecting Yourself When Managing Infected Plants
Since RRD does not pose a human health risk, the necessary precautions focus on preventing physical injury and stopping the virus from spreading to other roses. When handling an infected bush, wear thick gardening gloves and long sleeves to protect your skin from the excessive, pliable thorns characteristic of the disease. The physical removal of the entire infected rose, including the root ball, is the most effective management strategy.
All plant material, including roots and fallen debris, should be immediately bagged and sealed in a heavy-duty trash bag. This disposal method prevents the mites from escaping and being carried by the wind to nearby healthy plants. It is important to send the material to a landfill and never attempt to compost or chip the plant matter, as this will not kill the virus or the mites.
After removing the plant, all tools, such as pruners or shovels, must be disinfected to kill any mites that may have hitched a ride. A simple wipe-down with a household disinfectant, an alcohol solution, or a bleach solution will sanitize the tools before they are used on healthy plants. Additionally, washing your clothes and hands after working with an infected rose helps ensure no microscopic mites are transferred to other parts of the garden.