Q: I was at a nursery and mentioned to a staffer that one of my roses looked like it had rose rosette disease. He asked if I was sure it wasn’t witch’s broom. It’s important to know because treatment for the two conditions is different.
A: Witch’s broom and the abnormal growth caused by the rose rosette virus appear similar but they are not the same. Witch’s broom is usually found on conifers. It is characterized by a mass of twigs originating from the same point on a branch. On roses, the only thing similar would be when a rose has accidentally been sprayed with glyphosate, not a virus infection. This herbicide injury is characterized by tiny yellow leaves clustered in balls up and down the stem. As you know, rose rosette disease has several simultaneous symptoms: multiple shoots, excess thorniness, deep red foliage, and malformed flowers. Keep a close eye on your suspect rose. If more rose rosette symptoms develop, remove it completely.