Rose rosette virus samples have started coming back into the office so I thought it would be a good reminder of what to look for when scouting your roses.

This disease has been known in North America for decades, but it seems that it has become more common in our area over the last two years.

Symptoms can vary and may include elongated flexible shoots, the proliferation of shoots leading to a “witches-broom” appearance, excessive development of thorns, leaf deformation, retention of juvenile red coloration in shoots, and flower abnormalities. If you see the “thorniness”, then you can be confident you have rose rosette. Not all symptoms may be present in any given plant. Shoot proliferation and leaf deformation can also be caused by accidental exposure to low doses of the herbicide glyphosate (Roundup), so if you observe this symptom do some sleuthing to see if herbicide drift might have occurred.

Rose rosette is caused by a virus that is transmitted by the microscopic eriophyid mite Phyllocoptes fructiphilus. They lack wings but can be carried on air currents.

There is no chemical control for plant virus diseases. Since viruses become systemic in their hosts, pruning may or may not be effective. It has been noted unpruned roses tend to have a greater chance of rose rosette. Removal of infected plants is the best alternative. You should bag the rose before digging, to reduce the chance that the mites will scatter on the wind and take the virus to nearby plants. Remove enough of the roots so that the infected plant does not re-sprout. Also, remove any nearby weedy multiflora roses that may be serving as a host plant to mites and potentially the virus. It may be best not to plant rose bushes next to one another since the mites could easily move from plant to plant.

Rose rosette does not affect other kinds of plants. More encouraging is that some rose species are resistant, including the native Rosa setigera and Rosa carolina.

For more information on rose rosette or any gardening questions call the Wilson Extension Master Gardeners at 252-237-0113 or email at wilsonemgv@hotmail.com.