Rose Rosette Disease

Rose Rosette Disease (RRD) is one of the most destructive diseases of roses (Rosa spp.), especially across North America. It is caused by the Rose Rosette Virus (RRV), a member of the genus Emaravirus with a genome of seven single-stranded RNA segments.

The virus is not readily spread by casual mechanical contact. Instead it is carried mainly by a microscopic eriophyid mite, invisible to the naked eye (about 140–170 micrometres long, with only two pairs of legs). The primary vector is Phyllocoptes fructiphilus; a second species, Phyllocoptes arcani, has recently been confirmed to transmit the virus as well. The mites shelter in buds, leaf axils, petioles and at the base of new shoots; they disperse on the wind, on clothing and on other insects, and need less than an hour of feeding to transmit the virus to a healthy plant. RRD is also spread by grafting from infected stock.

Note for growers in Vietnam: Rose Rosette is chiefly a North American problem and is not widely reported in Vietnam / South-East Asia. Be especially cautious with imported planting stock. If you see similar symptoms, the more likely cause is herbicide damage (see below) or another disorder — but genuine RRD must be dealt with decisively, because there is no cure.

There is no cure. Once a plant is infected, no chemical can remove the virus, and pruning out symptomatic parts is ineffective because the virus is systemic and persists even in the roots. The task is to remove infected plants early to protect the rest of the garden:

1. Dig out the entire infected plant, including all of its roots — do not simply prune off the symptomatic canes.
2. Bag the plant sealed and destroy it (burn or landfill); never compost it or use it as mulch.
3. Clean and disinfect tools (70 % alcohol) after contact with a diseased plant to guard against surviving mites.
4. Reduce mite pressure on surrounding healthy plants with horticultural oil or a miticide (note: efficacy against eriophyid mites is not firmly proven — this is only a support measure and will not save an already-infected plant).

• Use clean, disease-free stock: buy only from reputable sources; never graft or take cuttings from a plant showing symptoms.
• Remove nearby wild roses: clear Rosa multiflora and other wild roses within about 30 m (especially upwind), as these harbour both the mites and the virus.
• Space plants and mix plantings: keep plants from touching to limit mite movement; interplanting roses with non-roses is better than a rose monoculture.
• Scout regularly: inspect for witches' broom, distorted red shoots and dense red thorns so infected plants can be found and rogued early.
• Resistant types: most commercial cultivars are susceptible; some wild species (R. arkansana, R. carolina) and the cultivar Stormy Weather show fewer symptoms.