What Is Rose Rosette Disease?

Rose Rosette Disease (RRD) is endemic to North America.  In the past few decades, it has spread from its source in the western part of the continent, through the Mid-West to the East coast. The disease initially spread in the widespread naturalized Rosa multiflora.  More recently, the disease has spread onto garden roses and now threatens to decimate the US rose industry. Garden roses are a cornerstone of the multi-billion dollar nursery and landscape industry and annually generate ~$400 million wholesale value of domestic bare root and container production in the USA. RRD is caused by a novel plant virus of the genus Emaravirus, the Rose rosette virus (RRV), which is transmitted by wind-blown eriophyid mites (Phyllocoptes fructiphilus). Unlike other rose diseases it can kill a rose within two to three years of infection. Although this disease has been known for many decades, the causal virus was only identified in 2011.  Symptoms of the disease can vary with rose cultivar, but commonly include proliferation of lateral shoots causing a witches broom symptom, unusual thorniness and reddening of the shoots, crinkling and rugosity in the leaves, and distorted flowers which lead to stunting, defoliation and eventual death of the plant.  Besides being spread naturally via the mite vector, graft transmission is also possible.  Mechanical transmission is considered unlikely, but may be possible under certain conditions.  This disease epidemic has led to a research-industry collaboration which is working towards better diagnostics, optimal management strategies, widespread educational efforts and the development of resistant rose cultivars.