Plant Problem Diagnostic
Rose Rosette Disease
The short answer
Rose rosette disease (RRD) is caused by the rose rosette virus, which is spread by a tiny, wind-carried eriophyid mite too small to see. It affects roses, and multiflora rose and dense modern landscape roses like Knock Outs are especially hard-hit.
The telltale symptoms are a witches' broom (a dense cluster of many shoots), abnormally red and distorted new growth, strap-like leaves, thickened succulent stems, and a striking overabundance of soft, pliable thorns crowded along the stems. Seeing that thorniness plus witches' broom is a strong confirmation.
There is no cure and the virus is systemic, present throughout the plant including the roots, so you cannot prune it out. Extension guidance is unanimous: remove the entire infected plant, roots and all, bag it, and throw it away rather than composting, to keep the mites and virus from spreading to nearby roses.
How to recognize it
Clemson Extension lists the characteristic signs: new growth with many branches forming a witches' broom, stems with an overabundance of pliable thorns, shoots and foliage with an abnormal red color, and stems that appear thick and succulent. The excessive thorniness is particularly diagnostic; healthy new rose growth may be reddish, but it does not carry dozens of extra soft thorns packed into a short length of stem.
Distinguish RRD from things it can mimic. Normal new rose growth is often red and then greens up, and herbicide drift can also distort growth, but neither produces the crowded witches'-broom of shoots with dramatically increased thorns. If you are unsure, your county Extension office or a plant diagnostic lab can help confirm before you remove a valued plant, though the combination of witches' broom, red distortion, and thorn excess is usually conclusive.
The vector and why there is no cure
The disease is spread by an eriophyid mite (Phyllocoptes fructiphylus), which the Missouri Integrated Pest Management program notes is less than 1/200 inch long, far too small to see, and moves easily on wind currents. The mites feed on tender stems and carry the virus from plant to plant. This is why RRD often spreads through a bed of closely spaced roses.
Once a plant is infected there is no treatment. Clemson Extension states that infected plants are not curable and that the virus is systemic, moving throughout all parts of the plant including the roots, so it cannot be pruned out. Cutting off a symptomatic branch does not save the plant, because the virus is already present throughout.
Removal protocol
Remove the whole plant, including the roots. Clemson advises disposing of all plant material, roots included, because roots left in the ground are still infected and can resprout into a new infected plant. Bag the plant and put it in the trash; do not compost it, since that can keep the mites and virus in your garden.
A practical sequence: bag or wrap the top growth before digging to keep dislodged mites from blowing onto nearby roses, then dig out the crown and as much of the root system as you can. You can replant the spot with non-rose species right away, but avoid replanting roses there until all diseased roots have been removed. To protect remaining roses, keep plants spaced so canopies do not touch, which slows mite movement between them.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Clemson Extension - Rose Rosette Disease: FAQs and How to Identify It — Symptoms include witches' broom of many branches, an overabundance of pliable thorns, abnormal red shoots and foliage, and thick succulent stems; the primary vector is an eriophyid mite; infected plants are not curable and the virus is systemic through the roots and cannot be pruned out; dispose of all plant material including roots because roots left in the ground stay infected and can resprout.
- University of Missouri Integrated Pest Management - Rose Rosette Disease — Rose rosette is caused by a virus vectored by an eriophyid mite (Phyllocoptes fructiphylus) less than 1/200 inch long that moves on wind currents; early symptoms include excessive thorniness, distorted buds, and strapped leaves, and infected plants should be removed.