Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Knockout Roses took the South by storm as they bloomed happily without requiring treatment for black spot fungus. Sadly, they and other garden roses are falling prey to rose rosette virus. Infected plants can have reddish stems, misshapen leaves and stems, and other growth abnormalities. A tiny, 1/200dredth of an inch long, eriophyid mite spreads the virus if it feeds on your roses. They’re often blown by wind from wild, invasive multiflora roses which were introduced from Asia as living fences to control livestock. Sprays will not protect plants. If your plant is infected, all you can do is dig it up completely, roots and all, and dispose of it to prevent mites on that plant from moving to other roses in your landscape. If multiflora roses are growing on property you have access to, removing them can reduce the mite population.