My knockout roses appear to have Rose rosette. Is there anything I can do or do they need to be removed? Also, my next door neighbor has knockouts, so is there anything she can do to protect her roses from this mite?
Thanks so much!
Tarrant County Texas
Unfortunately, rose rosette is caused by a virus and the current extent of our (scientific) knowledge is that this disease problem cannot be remediated.
The current recommendation is that rose rosette diseased plants should be removed to reduce potential virus reservior sites for the eriophyid mites (which is believed to transmit the virus).
For your neighbor, best approach is to currently treat for the mites. For a homeowner, this may include using horticultural oils as a protectant and/or product containing imidocloprid (ie. Bayer Advanced Rose & Flower care- slow uptake and not shown to work very well). Horticultural oils would serve as deterrents but needs to be applied frequent to maintain protection. Also, care should be taken when using oils because misuse can result in "burnt"/damages roses.
You can also get additional information at your local Texas A&M AgriLife Extension county office in Tarrant county (http://tarrant.agrilife.org).
If also possible, please contact me at the Texas Plant Disease Diagnostic Lab as we have a project currently ongoing to validate a genetic (pcr) detection method and are looking for suspect samples.