By Pat Johnson, Contributor
Rose rosette is a lethal disease that affects roses. There is no known cure for it. It has been around for more than seventy years, first noticed in Canada in 1941, and again in Wyoming in 1942. Over the years, it spread to other states and was detected in East Texas in 1990 and in the Dallas-Fort Worth area in 1995. It is now confirmed to be in Bell County.
According to “Rose Rosette Disease Demystified,” a paper about rose rosette from Texas A&M, symptoms of rose rosette include witches broom, malformed flowers and leaves, excessive thorniness, extreme red discoloration of plant tissue, lateral shoot elongation, and enlarged thickened stems.
Not all rose cultivars and types will have all of these symptoms.
Rose rosette is a virus that is spread by eriophyid mites. Eriophyid mites have four legs and are yellow to brown in color. These mites are not visible to the naked eye; they are less than 1/200 of an inch long, which is about three to four times smaller than an average spider mite. These small mites move easily with wind currents. One can unknowingly obtain an infected plant from a nursery or other plant outlet.
The affected rosebush will definitely be stunted and is more likely to die. Because it harbors the virus and the mites, it is best to remove the plant and its roots completely and immediately before rose rosette has a chance to spread any further. Bag it at the site and dispose of it in the trash. Do not put it or any of its leaves in the compost pile. If plants are touching, the mites can simply walk from one plant to another.
“When you have a problem it is best to nip it in the bud,” said Dr. Kevin Ong, a Texas A&M University plant pathologist who is instrumental in research involving rose rosette, In a seminar, he
stressed these steps.
1. Remove confirmed and/or symptomatic plants early after observation including roots (bag and discard; do not compost).
2. Treat adjacent plants with miticide to reduce the probability of transmission by eriophyid mites (use abamectin or horticultural oil). Please note: this will not stop the virus if it is already in the plant.
3. Remove any wild roses in the vicinity of cultivated roses.
4. Monitor (weekly) for symptoms and act quickly when and if symptoms are observed.
The most important is that if you see symptoms, act quickly. Extensive research is being performed about this devastating disease in the rose population. There are several websites that contain information about rose rosette, including www.roserosette.com.
“This problem will not go away,” said Ong. “Gardeners have to be diligent in helping to control the spread of rose rosette.”
At this time no rose variety is immune. All rose varieties can get rose rosette. The only sure way to diagnose this dreaded rose disease is to have it pathologically tested.
If you suspect you might have rose rosette on one or more of your rose bushes, contact Bell County Master Gardeners at 254-939-5305. One of our certified “First Defenders” will be in touch with you.