Are your “Knock Out” roses getting hit hard with disease? If so, this could be the reason. “Knock Out” roses are widely used in both residential and commercial landscapes due to providing showy and continuous blooms! They requiring very low maintenance and you do not need to spray for black spot disease.
However, recently we have met with two different customers, one is a commercial office park in Tucker and the other is a homeowner in Alpharetta, who both have “Knock Out” rose with similar symptoms. They have found that they have abnormal red discoloration of shots and foliage, witches broom (prolific clustering of small shoots), and distorted or dwarfed leaves.
If your “knock out” roses are having similar issues they might have a disease called Rose Rosette. It is a deadly threat on your roses and one that doesn’t have a treatment or cure. Rose Rosette is caused by a virus and it eventually spreads internally to every part of the plant. If you catch it early and promptly remove the bright-red shoot cluster by cutting through healthy green wood – it may help save your roses. Unfortunately, once a rose gets full blown rose rosette disease the plant cannot be saved. The best course of action is remove the entire plant including roots, bag the plant and remove from your landscape. Do not compose the plants. Either burn the plant or send it out with the garbage.
The virus travels on an extremely tiny eriophyid mites, Pyhllocoptes fructiphilus. This is not the type of mite you can see with the naked eye and the mite itself does not kill your roses. These mites are wingless and can be blown in with the wind. They can crawl from one plant to the next or attached themselves to other insects. Getting rid of the plant completely will help prevent the virus from traveling!