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Rose rosette disease (RRD) was first reported on the North American continent in the early 1940s. In 2011, the causal agent of this disease was identified and described—the Rose rosette virus (RRV). In the last 10 years, RRD has gained widespread notoriety because of disease symptoms appearing on many roses which are used frequently in landscape plantings, both commercial and residential. Much of the prior scientific work on this disease was carried out on the multiflora rose. Currently, the disease issues are on cultivated roses within which no cultivar has been confirmed to be resistant. There is an information gap in our knowledge of the pathogen, vector, and the disease on cultivated roses. Our goals for this project are to seek and identify potential disease tolerance or resistance in roses and increasing public awareness and knowledge of RRD with the purpose of reducing the disease spread with best management practices. Outreach and volunteer recruitment are key activities used to provide scientifically sound information, to establish the current disease range and to actively gather observational reports of RRD to identify resistant rose sources. Elements of these activities include educational meetings, factsheets, posters, and workshops where RRD symptoms recognition is emphasized. A web-based reporting tool was developed to capture observations from volunteers while continually keeping them engaged. It is hoped that through outreach and the collective monitoring effort, researchers will have access to information that contributes to a better understanding of RRD and will find disease-resistant roses that could be used in breeding programs for the continued enjoyment of roses.

Rose rosette disease (RRD) whose causal agent, the Emaravirus Rose rosette virus (RRV), was only recently identified has caused widespread death of roses in the midwestern and eastern sections of the United States. A national research team is working on the detection and best management practices for this highly damaging disease. Unfortunately, little is known about the host plant resistance to either the causal viral agent or its vector, the eriophyid mite Phyllocoptes fructiphilus. Thus far, the only confirmed resistance is among Rosa species. Of the over 600 rose cultivars observed, only 7% have not exhibited symptoms of RRD. Replicated trials are in progress to confirm resistance and/or susceptibility of ≈300 rose accessions in Tennessee and Delaware. Rose is a multispecies cultivated complex that consists of diploid, triploid, and tetraploid cultivars. The basic breeding cycle is 4 years with a 3-year commercial trial coupled with mass propagation before release. Thus, if only one breeding cycle is needed, a new cultivar could be produced in 7 years. Unfortunately, for the introgression of a new trait such as disease resistance from a related species into the commercial rose germplasm, multiple generations are required which can easily take two decades from the first cross to cultivar release. Research is ongoing to develop a rapid selection procedure for resistance to RRD with the aid of molecular markers associated with the resistance. Such an approach has the potential of reducing the breeding cycle time by 50% and increasing the efficiency of seedling and parental selection manifold, leading to commercially acceptable rose cultivars with high RRD resistance in less time and with less expense.

The eriophyid mite, Phyllocoptes fructiphilus, vectors the causal agent, Rose rosette virus (RRV), that results in rose rosette disease. Parts of the southeastern United States have remained free of the disease, except for infected plant material introductions that were eradicated. A survey of sampling points through Alabama, Georgia, and Mississippi (n = 204) revealed the southeastern border of RRV. The presence of RRV in symptomatic plant tissue samples (n = 39) was confirmed by TaqMan-quantitative reverse transcription polymerase chain reaction (RT-qPCR). Samples were also collected at every plot for detection of eriophyid mites, specifically for P. fructiphilus. Three different species of eriophyid mites were found to be generally distributed throughout Alabama, Georgia, and Mississippi. Most of these sites (n = 60) contained P. fructiphilus, found further south than previously thought, but in low populations (<10 mites/gram of tissue) south of the RRV line of incidence. Latitude was found to be significantly correlated with the probability of detecting RRV-positive plants, but plant hardiness zones were not. Plot factors such as plant size, wind barriers, and sun exposure were found to have no effect on P. fructiphilus or the presence of RRV. The reason for the absence of RRV and low populations of P. fructiphilus in this southeast region of the United States are unclear.