Hi Cathy,
I attended the Rose Rosette Summit last year in Delaware and and leading virologists, those studying eriophyd mites, breeders, nursery professionals, plant disease clinic directors, etc. were present. We brainstormed our resources and plan of direction for research and funding sources. We applied for a Specialty Crop Research Initiative (SCRI) grant and are waiting for the announcement. David Byrne coordinated that grant. Other grants are out for studying the virus and mite and interaction with roses.
Throughout the discussions we learned where multiple people are in different areas of research that would be of value to the effort. Kathy Zuzek, Stan Hokanson, and my work with breeding behavior of R. setigera, a possible source of resistance, was also highlighted. Kathy and I wrote an article for the ARS annual for this fall and have a paper in Floriculture and Ornamental Biotechnology. Here are some things that may be helpful that aren’t filtered down into publications yet as far as I’m aware:
With PCR testing (typically much more sensitive than ELISA) the presence of the virus could not be detected early on outside of the brooms. This suggests it moves relatively slowly and if someone is very aggressive may be able to cut them off asap and save their plant. This May I learned from a good friend in Texas that manages a part system that she did that with some beds cutting back some recently infected roses hard and this year so far they are growing well and looking clean without new brooms forming. This may suggest that if you have hips on a clean looking section of your plant there is a chance you can have clean seedlings.
The mite puts its mouth parts about 18 microns into tissue and loves soft shoot tips and loves feeding on tender opening flowers. This is where we find infections first and need to look closely. Pruning to encourage lots of new growth and growing roses that branch and flower continuously obviously helps create more potential infection points through the growing season.
At the meetings it was discussed that a typical mature R. multiflora can produce 500,000 seeds per year. As infected plants die the idea is that the clean new seedlings would likely help keep a ready supply of R. multiflora and RRD going with new infections. The idea of RRD effectively or at least quickly eradicating R. multiflora seemed slim.
The use of miticides to control RRD needs to be trialed more, but likely shouldn’t hurt in RRD transmission if people want to try something. The idea is that with eriophyd mites being blown in periodically, how much do they need to feed before transmitting the virus? Will they be able to transmit it as they feed on treated material before they die? Since they get into tight spaces, contacts will likely be much less effective than systemic miticides.
Perhaps the increasing trend of finishing rooted rose liners at regional nurseries and distributing them wholesale is contributing to increased rates of RRD. During the season or more of production in pots on gravel beds if RRD is in the region plants may become infected and then shipped before they even show infections.
Some hope for the future:
Work is planned and under way by Mark W. and others for cultural means to limit/reduce RRD spread.
Roses are planted in test beds near infected R. multiflora to hopefully identify specific genotypes of species and hopefully cultivars that can be sources of resistance.
Work is being done to insert a portion of the virus genome backwards (antisense) into rose to create a GMO rose that should be resistant to RRD- much like what has been done for Plum Pox virus in some Prunus and also for a deadly virus in papaya. This technology saved the papaya industry. We’ll see how accepting the public is with a GMO rose. RRD has been documented in Europe (that was reported at last August’s Rose Research Symposium held in Germany) and they are very concerned about RRD too. They tend to have a much more limiting approach to GMO’s than the US. Hopefully those that own the patents for the process, etc. (likely a utility patent will be sought) would be willing to license the technology to other breeders.
The map in your link included all of MN and WI. I had RRD by my parents in central WI about 6-7 years ago. It infected and killed my R. multiflora rootstock hybrid bred by Dr. Buck, but thankfully none of my other roses suffered. I hope RRD stays out of the Twin Cities and my rose gardens. It seems as one goes north R. multiflora is less common to non-existent, so hopefully that will help reduce the spread.
I wish you the best in battling RRD and others too and hope I don’t get it in my garden. I’ll start a new message string regarding RRD and sending samples to a grad student I spoke with Friday so it doesn’t get lost in this thread.
