Rose Rosette Virus--Can it be Beaten?
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Q: Back in 2012, LeeAnn in Burlington NJ wrote: "I have two twenty-five-year-old roses. They have "wild areas" of 'unusual bunching' and twisted and distorted leaf growth. I Googled it and it looks like Witches Broom. What if anything can I do?"
Q 2--also from 2012, Gabrielle in Newtown PA wrote: "I've had a gorgeous climbing rose in front of my house for over 10 years with no abnormal growth, putting out white to pale pink roses in abundance. But this season I noticed weird clusters with different shaped leaves, color, and growing habit. I cut out the areas where this occurred. Do you know what this is?"
A. First--why am I using questions from 2012? Two reasons. The first is that I had to search back that far to find people who obviously had the problem that is today's topic There were a lot of recent questions that might have been about today's topic, but these two nailed it. Second, there were a lot of similar questions from that season, and I suspect that this time frame is when this disease really exploded in the mid-Atlantic region. And third, if you saw my office, you'd realize that seven years isn't a long time for me to get around to doing anything.
Yes--that is three reasons. I wanted you to know up front that you're about to take advice from a guy who can't count. To three.
All seriousness aside, the condition is called rose rosette virus. It's been around since the 1940s, but has occurred with frightening frequency over the last ten years or so. "Witches' Broom" is a perfect generic description, as those words refer to a 'deformity' that can take many shapes and affect many woody plants. Witches' Brooms are often caused by a disease or mites, and in this case, the scientific consensus is that both are to blame.
A tiny little mite whose name I cannot pronounce blows in on the wind, feeds on the plant tissue and transmits a virus that causes the weird distorted growth. (This is not uncommon. Many insects, like the cuke beetle, do more damage transmitting disease than by feeding. Oh--and for the record: Mites are not insects; they are arachnids, like ticks and Spider-Man.)
2012 was also right around when I noticed the growth on one of my roses: a French landscape rose marketed under the "Flower Carpet" brand name. The flowers it produces are small, but one well-established plant will typically pump out thousands over the course of a summer. One of my favorite tricks was--and still is--to give people "a bouquet on a branch": three dozen roses blooming on a single stem. Very cool.
I also have a lot of "wineberries" (delicious relatives of raspberries that grow wild all through the mid-Atlantic) growing in the same area; and at first, I thought that the plants had somehow crossed; that I had wineberry canes growing on my roses because this strange new growth kind of resembled the baby wineberry canes as they emerge from the earth.
Pretty soon I realized this was probably as wrong as most of my answers on a true or false test, so I pruned off the weird looking stuff--unaware that the condition is considered fatal and that I was supposed to pull out the whole plant, trash it and call it bad names.
The next season, the weird shoots came back, but this time I pruned them off right away. The following year, maybe one cane showed the signs. Snip. Snip. And that was it. Yes, this seems too simple, but in my garden, simple often works.
Then last summer, I was invited to give a talk in Fayetteville North Carolina. One of my sponsors, a hospital group called First Health had a "healing garden" for people and their families experiencing serious medical issues and a "hospice garden" in another location. The Healing Garden looked great; roses here and there, but there were lots of other plants as well, and the roses looked fine. The Hospice Garden was itself in hospice. Designed to be a "rose garden", it was wall-to-wall roses, all of which seemed to be infected to some degree.
I was asked for suggestions.
I said to dig everything out. Rose bushes that were completely infested were to be destroyed. Bushes with small symptoms were to be pruned and 'heeled in' (planted temporarily) in another location. Then the crappy wood mulch in all the beds was to be removed and replaced with the yard-waste-based compost that helps roses thrive.
Then any healthy roses were to be slowly reintroduced--but the design could no longer be 'all roses all the time'. Each rose had to be surrounded by a lot more airflow and then something non-rose--like a cute little evergreen or some nice statuary. No roses touching each other. And have a fast hand with the pruners if rosette shows up.
No miticides! The best answer for bad mites is not nasty poisonous chemicals, but the good mites that go after the baddies like The Lone Ranger in the Old West--so don't kill the good guys (eh, the good arachnids)!
More airspace. More diversity--both in types of plants and types of roses. Compost mulch. No chemical fertilizers, which themselves can cause rapid and abnormal growth.
Let's see what happens, shall we?