The author is with the Cornell Cooperative Extension of Albany County.
Blights, fungus and insects from Asia move over to make room for the latest threat to our backyard gardens: a viral disease that is spread by mites that attacks all types of roses. Rose Rosette Disease is not new but it is new to our area and it seems to be making its mark rather quickly so let’s try to understand why. This disease was first identified in the 1940s but the causal agent was not pinpointed until 2011. As is often the case, many factors are at play but the main culprit is a tiny eriophyid mite that also causes rose leaf curl. The microscopic mites travel on the wind or on birds or insects in search of rose plants. As the mites feed on the rose leaves, they spread a virus that causes bizarre symptoms such as rapid elongated growth that is reddish in color with many thorns, malformed buds and an excessive number of new shoots or witches broom. Close observation will easily reveal the disease – it is easy to spot. The virus is also spread by pruning tools, and so careful disinfection of pruners between plants is important. Grafted rootstock can also harbor the virus so inspect all potential rose purchases carefully. Management is total removal of the plant as soon as the virus is detected. Since this is not a soil borne pathogen, roses can be planted in the same area.
One of the main contributing factors to the spread of Rose Rosette is the invasive Multiflora rose. A native of Asia, it was introduced in the 1800s as an ornamental and as rootstock to gain hardiness for more tender roses. In the 1930s its use spread to conservation as erosion control and for reclaiming land used for strip mining. Time has revealed that these very qualities also make it a horrible weed that proliferates everywhere. This rose is very susceptible to Rose Rosette disease and considerable numbers are being killed by the virus. It takes about two years for the virus to kill a plant and so during that time the mites multiply and so the Multiflora roses become a source of inoculum for the virus.