What is Rose Rosette Disease?
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I have seen the look on the face of gardeners when somebody mentioned ROSE ROSETTE DISEASE. It seems that few gardeners have heard about it. There was an article about it years ago on the American Rose Magazine, Jan. 2003 issue. Below are excerpts which are very important for us to know.
“Rose Rosette Disease (RRD) is a growing danger to ornamental roses in the eastern half of the United States. This virus-like disease is contagious, incurable and almost always results in the death of the rose. No ornamental roses are known to be immune. A puff of wind can drop an infection carrying mite onto a rose at random. Symptoms may not appear for weeks, and the disease may not be recognized for months. In that time, RRD may spread in a garden. We cannot prevent infection, but if we recognize symptoms early, we can minimize the impact of RRD.
Early symptoms may include foliar distortion and susceptibility to powdery mildew at a time when other roses are not affected. The reddish purple color, which is common on spring and fall growth on many healthy Hybrid Teas is often associated with RRD. On healthy roses, the color “disappears” gradually as the leaves and canes age. On RRD infected roses, the color persists.
Leaf shape varies from the norm. Some are thinner in shape and barely resemble leaves. A shortened distance between leaves on a stem or cane is another symptom. Oddly colored veining consisting of a bright red to dark red pattern (which is also called mosaic pattern) following the veins in leaves has been reported as an early symptom of RRD.
Excessive thorniness in a rose that normally has two or three prickles per inch may have 50 or 100. Canes may appear swollen and have increased caliper. Thick new canes growing from a significantly thinner, older, less thorny cane and rapid elongation of new canes is also common in roses with RRD. Cane growth in a spiral pattern should arouse suspicion. A mass of scraggly, contorted twigs emerging from a single leaf axil is another symptom. Symptoms of RRD only appear in new growth, not old. In that way, RRD differs from other rose diseases which affect existing leaves and canes.
RRD-infected roses may not bloom, but new infection may allow some normal growth, only to affect new leaves (size) and new buds (deformed). When they bloom, the resulting blooms will not look like blooms on healthy plants. Often, the petal count is reduced and the petal shape and margins changed. Seldom is the petal color the correct color for that cultivar. Often blooms gone wrong are the first characteristic because we enjoy roses for their blooms.”
If the above symptoms are present, prune the infected area and watch the growth. If it has RRD, it will never get better. Discard the rose and save your garden. It could infect your whole rose garden. Hopefully extreme cold weather will kill the mites that are spreading the disease around.