Roses infested with rose rosette disease take on a pinkish-red cast, develop more thorns than normal and form witch’s broom. Photo courtesy Linda Kimmel
There’s a rose disease showing up in Indiana and it’s deadly. Called rose rosette disease, sometimes referred to as RRD, is a killer, affecting the $400 million domestic rose production industry.
The disease was first detected in 1941 in western states, and had spread to Tennessee by 1994, affecting primarily multiflora roses (Rosa multiflora or R. poliantha), which are considered an invasive species. A wingless mite, 1/200 of an inch long, feeds on an infected rose, gets blown by wind to our gardens, bites our roses and wham, infected plants.
“My roses became infected at the end of last year,” reports reader S.M. “I cut them off and hoped they would be fine this spring. Had no idea what was causing the leaves to turn dark red then brown, and the tip of the buds to twist, curl and become deformed. The entire bud area turns fiery red and stunted.”
That pretty much describes what people see on infested plants. The virus causes development of more thorns than usual and a clustering of branches, called witch’s broom.
“I live on the southern edge of Marion County, surrounded by farm fields and have RRD bad,” said Linda Kimmel, district director of the Illinois-Indiana Rose Society. “About eight to 10 percent of my roses get infected every year and have to be removed. Some rose growers who live in town or suburbs, not so much of a problem.”
Tom Creswell, director of Purdue University’s Plant and Pest Diagnostic Lab, which tests for the virus, has seen only a handful of queries about the disease. Widespread in Tennessee, Texas and Oklahoma, our planting habits contribute to the spread of the disease, he said.
“Planting large drifts of the same variety of rose, or just large drifts of any rose, in public spaces increases the risk, if the disease gets started,” Creswell said.
Unfortunately, rose rosette disease is fatal. There is no cure. Miticides do not work on the mite that spreads the virus. Remove and destroy roses as soon as you notice the disease. Once infested roses and their roots have been removed, you can replant roses.
Kimmel said research shows that Knock Outs are no more vulnerable than any other rose. It’s just that there are planted everywhere, from gas stations to road medians to our gardens. The virus can be dormant in roses for two years before symptoms appear.
Rose Show Sept. 26, 2015
La Quinta Inn & Suites South, 5120 Victory Drive (I-465 & Emerson south), Indianapolis. The Rose Show is open to the public at noon and free. Registration is $40 for the full event, which includes lunch and programs by Stephen Scanniello, curator of Rockefeller Rose Garden in New York, and Bruce Monroe of Delaware, who will give a program on rose photography and how to improve our rose photos.