Rose Rosette Disease - Part 2

a. Monitoring your roses for disease. Rose Rosette does not spread rapidly throughout the rose. Likewise, the mite and its offspring don't always balloon from cane to cane. In fact, mites frequently breed in one protected area and their offspring may remain nearby simply because the conditions favor their development. That is, relatively cool, moist conditions exist with sufficient plant material to provide food for promoting future mite generations.

Therefore, if your rose has several good canes and shows the disease on only one cane, you might be able stop the spread of the disease by quickly removing the offending cane in its entirety. That means not just the stem or lateral showing the disease, but the entire cane to which it is attached. Furthermore, the remainder of the rose and those roses in close proximity, as well as the surrounding soil and structure, should be monitored and treated for mites.

Dr. Philley adds, this is a "long shot" treatment, but it may work if the disease is caught in time.

b. Miticide applications. According to Dr. Philley, only one miticide proved effective at controlling Phyllocoptes fructiphilus - Dimethoate (Cygon®). Although carbaryl (Sevin®) was also tested, it was only partially effective. Dimethoate or carbaryl should be applied as per label directions, despite the fact this pest is "no ordinary mite."

One should exercise extreme caution when using dimethoate, however. As you can surmise from the application rate on the label, it is highly toxic. Please check Oregon State University's Extension Toxicology Network report before applying this pesticide. Unfortunately, carbaryl isn't much "less toxic" than dimethoate. You can read a summary here.

Are there any other alternatives? Well, possibly. But there is no efficacy data which suggests these alternatives may help curb the disease.

a. Diversified plantings. Mites frequently pass between plants by crawling or ballooning from one plant to another. Evidence suggests pests and diseases are lessened when intermixing different species of plants vis-a-vis using monocultural gardening techniques. Consider interplanting your roses among other landscape ornamentals instead of grouping all of your roses into one area.

b. Isolating new plants. Whenever purchasing a new plant from an unknown nursery, either directly or through the mail, consider potting it up in a container for a few months to determine if the plant is pest and disease free. The plant should be confined to an area away from other plants, especially if they are from the same genus.

c. The copyright of the article Rose Rosette Disease - Part 2 in Rose Gardening is owned by Mark Whitelaw. Permission to republish Rose Rosette Disease - Part 2 in print or online must be granted by the author in writing.