It sounds like an innocuous name--you might almost think it's a craft item made from the flower. But rose rosette is an extremely serious virus that can mean almost certain death for a rose.
If you're unlucky enough to have found a flush of too-vigorous, very thorny, curled and crinkly red foliage coming up in a cultivated rose, you've got rose rosette. This deadly virus doesn't respond to treatment; dig out the affected plant, roots and all, to save other roses in the garden. It's been said that if the disease is caught early, and the strange growth is cut completely out of the rose, there's a 50-50 chance that the rose can recover. But a lot of gardeners don't want to take the chance of risking their other roses and would rather get rid of it.
I'm one of those gardeners. Thanks probably to a multiflora rose or two in the vicinity (they act as the host for this disease), one of our favorite roses in the garden began showing the classic symptom last season: a witch's broom of burgundy-red growth that seemed to shoot up suddenly on one side of the plant. My husband and I didn't take long to ponder the problem; we dug out the bush. We'd rather lose one rose than to lose them all.
Every case of rose rosette doesn't have to look like that. The way the disease manifests itself depends on the variety of rose. Sometimes there's no flush of red stems and curled foliage but instead simply a lot of unusually soft thorns on a new cane; the thorns may stiffen in time. A cane may be thicker than the cane it springs out of. Or, the flowers may be distorted or discolored. Petals may be mottled instead of a solid color.
The disease is spread by the eriophyid mite, which usually picks up the innoculum from a multiflora rose. If you dig out all the old roots from the diseased plant, you should be able to plant roses in the same bed again. But don't leave a cut-down diseased rose lying around. Instead, bag it and remove it.
This disease means business.
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Photo courtesy of Bob Hartzler, Iowa State University
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