Rose rosette disease only affects roses. All roses, including the popular Knockout® family of roses, are susceptible to rose rosette disease.
What Causes Rose Rosette Disease?
While the disease itself is a virus, the culprits that transmit it to roses are eriophyid mites. They are yellow or brown in color, but you won’t be able to detect them on your roses because they are less than 1/200 of an inch long and can only be seen under a microscope. By sucking out the sap of the tender new growth—both buds and stems— eriophyid mites transmit the virus into the vascular system of the plant. Once the virus is in the plant, it moves to all parts, including the root system.
How Does Rose Rosette Disease Spread?
The invasive multiflora rose is most likely the original host plant of the virus, and it is highly susceptible to the virus. When feeding on an infected multiflora rose, eriophyid mites pick up the virus. The mites don’t fly; they are carried to other roses by wind or currents, human movement, animals, pruning tools, or grafting.
Identification
The earlier you detect rose rosette disease, the better. Thoroughly inspect your roses when new shoots emerge in the spring and do this regularly during the growing season as symptoms get more pronounced and spread throughout the plant. Not every rose shows all the symptoms, and the symptoms also differ depending on the rose species or variety. One thing that makes the identification of rose rosette disease tricky is that some of the symptoms, such as the typical witch’s broom appearance and distorted leaves, look similar to herbicide damage. If you can rule out that your roses were exposed to any herbicides, it’s more likely that you are dealing with rose rosette disease.
Rose Rosette Disease Symptoms
Deformed tightly clustered flower buds that look like rosettes, which gave the disease its nameDeformed and stunted flowers and/or abnormal flower colorElongated shootsContorted and stunted and/or yellow leavesDistorted clusters of new growth that looks like a witch’s broomNew shoots and leaves that are bright red instead of greenThick stems with lots of soft thornsCanes growing in spiralsReduced winter hardiness
How to Treat Rose Rosette Disease
Unfortunately, there is no treatment for infected roses, the only measure to take is to remove the plant with its entire root system. Pruning out the infected parts is not an option because eventually the remaining rose plant will die, due to the infection in the roots; in the meantime, it will spread the disease to neighboring roses. Because the virus spreads so easily, it is best to place the plant in a large garbage bag immediately at the location where you removed it, rather than carry the uprooted plant across your yard. Tie the bag shut and dispose of it in the trash. Do not compost a diseased plant or throw it on a brush pile. If there are any roots left behind in the ground, they might resprout. Make sure to remove them promptly.
How to Prevent Rose Rosette Disease
Because rose rosette disease cannot be cured, taking preventative measures is all the more important. Only buy roses from reputable sources and inspect the plants for signs of the disease. When planting, give rose bushes enough space between plants so they won’t touch each other even when they reach mature size. This not only prevents the mites from moving easily from plant to plant, but also provides good air circulation, which minimizes the risk of other diseases spreading between the plants. Remove any multiflora roses in your yard. And if there are any multiflora roses growing in the surrounding 100 yards, talk to your neighbors and offer to remove them. Getting rid of this highly invasive species is in everyone’s interest as well as benefitting your rose bushes. Eriophyid mites overwinter in flower buds and seed heads. For this reason prune any flower buds or seed heads by late winter or early spring and dispose of them in the trash. Disinfect your tools with a chlorine bleach solution (one part bleach and nine parts water) before moving to another plant. The mites are blown from plant to plant by the wind. Protecting your roses with a mechanical barrier against the prevailing wind cuts down on the risk of mites landing on them. Using leaf blowers has the same effect as wind so don’t use leaf blowers around your roses. After you have been exposed to a rose with the disease—either in your own yard or a multiflora rose that you removed from somewhere else—wash your hands, gloves, and clothes before approaching your roses again. The mites might stick to surfaces and because they are so small, you won’t even know they are there.
Replanting After Removing an Infected Rose Bush
If you removed an infected rose from your yard, replanting anything else but a rose in the same location is not a problem. Replanting roses, however, is a different matter. Even after thorough removal of all the roots, there might still be roots with the virus left in the soil. Wait for at least a couple of years before replanting another rose in that location.
