knockout rose gets knocked out
You are outside admiring your landscaping when you notice something different about your knockout roses. New, long, red shoots are protruding out from your otherwise normal looking plant. The flowers have bloomed and appear gnarled. What you are looking at is the effects of the virus known as rose rosette disease. The disease will continue to spread to all other parts of the plant. The knockout rose's health will continue to degrade and it will die.
...but wait, there's more! If that wasn't bad enough, the virus is spread by eriophyid mites. These mites are about the size of dust and simply go where ever the wind takes them. You read that right. Wherever the wind blows is exposed to the risk of rose rosette and all of their knockout roses dying. If the mites, which you can't see, land on your knockout roses and feed, they transmit the virus and your roses chance of survival drops substantially.
how to treat rose rosette
Well the short form of it is you can't treat it. Once the virus has entered the knockout rose, its there to stay. Your only chance of saving the plant is to catch it early remove the infected part of the plant by cutting well below the infected area, cutting into the healthy part of the plant. If you didn't notice the disease until it has infected the entire plant, here's what you do. Uproot the plant and dispose of it. Sorry, but there is no other options to save it.
Unfortunately, knockout roses are not exclusively the only rose the rose rosette damages. There are many other varieties susceptible to the virus so keep an eye out. All roses with the virus will display the same symptoms as the infected knockout roses.