Photo: Oklahoma State University Extension
Rose rosette disease is a condition that attacks roses, causing them to develop strange, deformed stems, leaves, and flowers. Rose species and rose hybrids are the only suitable hosts for the disease, with its primary host being the multiflora rose.
As of now, there is no cure for rose rosette disease, making it an incredible threat to the multiflora rose species and potentially to all cultivated roses.
Due to its inability to be cured, it’s important to know how to identify and control this disease.
What Causes It?
Rose rosette disease is caused by a virus, which is generally spread by eriophyid mites (Phyllocoptes fructiphilus). This tiny mite has no wings and primarily moves around by crawling or through air currents. They can also hitch a ride by clinging onto clothing and equipment.
The mite is native to the Western part of the United States and is one of the tiniest animals on earth. The mite picks up the virus by feeding on an infected plant and then transmits it by feeding on a healthy one.
If a healthy rose is close to an infected one, it’s much more likely it will become infected.
How Can It Be Identified?
The earliest symptoms of the virus include a red pigmentation present on the underside of leaf veins, which is then followed by excessive growth of thorns alongside the stems and accelerated growth of clusters containing reddish shoots, known as ‘witches’ brooms.’
Looking for any deformities can also help to identify rose rosette disease, such as crinkled, discolored leaves and/or flowers. Branches and shoots that come off the roses will begin to die, leading infected plants to become extremely vulnerable to damage caused by freezing temperatures and other diseases.
Smaller roses will die after being infected within two years, while larger ones may live up to five years.
Control Methods
If rose rosette disease has already infected your client’s plant(s), there is no effective treatment. Those who are breeding ornamental roses have attempted to create disease-resistant cultivars, but no ornamental rose is completely resistant to the virus so far.
If your customer’s plant has been infected, it is best to just dispose of it to prevent the disease from spreading.
Photo: Oklahoma State University Extension
An infected rose can spread disease to other potential hosts up to 300 feet away, making it incredibly dangerous when it comes to ornamental roses that are somewhat in close proximity of multiflora roses.
Despite how lethal it is once a rose is infected, there are ways to preventively control the virus.
Try not to use leaf blowers near roses. The mites that spread the virus can travel through the air current, potentially landing on a healthy rose and infecting it.
Try to prune roses in late winter or spring. Mites live within the buds and seed heads, so removing them can help eliminate the potential of spreading the disease.
Also keep roses in a more sheltered area to protect them from wind flow; this way, if mites are being carried by the air flow, this lessens the chance they land on your roses.
Eliminating any multiflora roses that are growing on your client’s property can also help to decrease the chance of roses becoming infected with the disease. Since multiflora roses are the primary hosts, the less of them there are, the less of a chance they will be able to infect healthy flowers.
Maintaining a good amount of space between each rose plant will also help to decrease the likelihood that mites crawl from plant to plant, controlling the infection.
