Part 1 - Ribs & Rosette

Part 2 - Death of a Noble Centenarian

Part 3 -“We have a problem with our roses ....”

Part 1 - Ribs & Rosette by Larry Peck (From the Oct. 2000 Holston Rose Society Newsletter)

One of the functions we attended at the Fall 2000 ARS Convention was a bar-b-que dinner called “Ribs & Roses” at the Atlanta Botanic Garden in downtown Atlanta. During the past year Ann & I have been learning about Rose Rosette Disease (RRD). We have read a lot and have driven many miles to study it in gardens and in the wild. We have taken hundreds of photographs and followed the disease on specific plants through the summer. Bottom line - although we still have much to learn we have learned a lot.

Much of the information written about RRD is misleading or incomplete, because the disease was observed in a only single class of roses or even a single cultivar during only one season. Most observations are based on limited studies in laboratories, or test gardens - not on real rose gardens.

One of the things we have tried to do this summer is to devise a list of subtle early symptoms that would alert a gardener to keep an eye on a particular rose and to know when to spray the mites to prevent potential spread from a suspect bush while it is under observation. This would reduce the chance of over reaction and killing healthy bushes simply because of a blind shoot or other false symptoms.

After spending the entire summer looking at hundreds of sick roses, including many different classes and cultivars we have gotten pretty good at recognizing subtle symptoms of RRD. Guess what? At the dinner, we found a ‘Fourth of July’ with RRD. Not the subtle symptoms we have been working on, but a blatant text book example. A four foot long ultra thorny (a hundred per inch) swollen (one inch diameter rather than 3/8 inch) cane with classic witch’s broom. There were two bud sprays that had not opened and the bush was no longer producing leaves on that cane. Those symptoms mean RRD has been there for a long time - too long - long enough to spread. We took lots of pictures of it and three other infected bushes.

Hundreds of our nation’s best rosarians walked past it and none noticed the sick bush. Once it was pointed out to them there was great interest, and the garden became a class room. That is, after all, partly what botanic gardens are for - education. We met people from around the country, many of whom are dealing with RRD in their areas.

One woman from Texas told of an 800 rose garden at a university near her that was completely wiped out by rose rosette.* RRD is not just another malady for rose growers to deal with. It is unlike blackspot or mildew for which we can spray. There is no cure. The arrival of RRD in an area especially an area with wild roses - can be viewed as a sort of climate change. A change to a climate which is not as condusive to growing roses. For that reason it will result in fundamental changes to our hobby. I hope we are not seeing the rose equivalent of the arrival of chestnut blight in the first half of the 20th century, but that possibility does exist. Chestnuts still exist - there are simply fewer of them restricted to limited areas.

Many people at the dinner had never heard of RRD, while other had read about, but never seen it. Several people, including a Consulting Rosarian (CR) from Staunton, VA had attended the ARS convention in St Louis at which a proponenant of the spread of RRD spoke. He assured the ARS members they had nothing to worry about. The CR knew about it, but had never seen it on a real bush. I’m glad he had a chance to see it, because he will be seeing a lot more of it soon. When we went up I-81 last May the Shenandoah Valley was white with the blooms of Rosa Multaflora the primary host plant of RRD in the wild. It will be in Staunton soon**.

Good food (Corky’s), good music (bluegrass), learning about roses, old friends and new ones. That’s what conventions are about even if the topic does occasionally turns away from pretty flowers.

* For the real story see "Multiflora Rootstock" in the FAQ's section of this book.

** It arrived in Staunton in Spring of 2002 - see Thornrose Cemetery in Chapter 15.

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Part 2- Death of a Noble Centenarian by Ann Peck

Roses come and roses go. But really old roses deserve to be a class unto themselves, to be cherished for their longevity. Two such roses were ‘Rosa roxbergii’ and ‘Seven Sisters’, neither that rare in gardens, but these two had lived in the yard of our farmhouse for at least a hundred years. A neighbor who died in 1999 at age 98 told us he remembered both from his childhood when his grandfather owned our farm; specifically, he remembered falling into ‘Seven Sisters’ when he was young and needed help to get out.

Click on Pictures to Enlarge

Above - is the bush which we removed.

At left - are blooms of 'Seven Sisters"

Neither rose was exceptionally vigorous. Trees grow a lot in a hundred years, and both roses grew in conditions that could at best be characterized as partly sunny. “Roxbergii’ got a reprieve when a small tornado took out a large tree that shaded part of the back yard. In gratitude it changed from blooming only in Spring to blooming Spring, Summer and Fall.

In 2000 we started learning about rose rosette disease. When we found a hillside with dozens of bushes of ‘Rosa multiflora’ infected with rose rosette disease about ten miles up wind of our farm, we decided to remove a ‘R. multiflora’ in our back yard (see Chapter 3 part 2) and to remove all the clutter saplings that grew at the bases of the old roses. Removing privet hedge with thick trunks that that had intergrown with the old ‘Seven Sisters’ was challenging while ‘Seven Sisters’ dug its paired thorns into us. Mimosa and hornbeam were also cut out exposing all parts of the rose for inspection. ‘Seven Sisters’ remained in the semi-sun and was beginnning to respond to removal of the trees that were intergrowing with its roots and stems.

That October, one cane of 'Seven Sisters' showed aberrant leafy growth. Three or four clumps of rosettes of leaves grew at very short internodal distances and hyper developed fringes on the sepals on a single cane. The leaves' undersides appeared to be tinted light pink. Other canes on that rose showed no comparable growth. After debate we chose to cut the cane back at ground level and to spray the remaining plant and “roxbergii’, sixty feet away with Cygon 2E. (This destroyed the saffron crop under 'R. roxbergii').

Chatter on the internet led to our decision. One report from Georgia reported saving a rose by cutting the only infected cane off of it. A second report by Field Roebuck referenced Dr. George Philley at Texas A&M who said 50% of roses could be saved. We took cuttings from a most distant and apparently uninfected stem and delivered them to a plantsman for propagation determined to at least save something of the rose just in case it couldn’t be saved.

One month after the first cane was cut off, we saw aberrant growth on a second cane. The growth was close to where the growth had been on the first cane, far from the ground, out on a ‘limb’. Justifying our decision to let it live, we cut that cane back and sprayed again. We hoped that the contagion had passed from cane extremity to adjacent cane extremity and we had stopped the spread before it reached the root and and from there to the rest of the bush.

December and January were colder than usual. February weather found higher temperatures and the beginning of normal growth on the rose. February 8 in the same part of the bush, additional distorted growth appeared. Let me remark that the growth was out towards the ends of the canes, and did not recur on the lower parts of the canes. This indicates the third and forth canes were infected by mites rather than by infection from the first cane via the root. On the ground, however, where the infected cane had been cut off earlier, there were two growth spurts in a bright strawberry red, with hyper-grown stipule margins and aborted leaves and growing not at all in the style of a basal break. The infection had gotten into the roots.

I had hoped that the disease was confined to the end of the canes and that the bush would survive. Had sunlight (rare in winter in Tennessee) not backlighted the new growth, it would have continued unseen for several weeks. The infected new growth emerged from the ground near where the first cane was cut off in October; this helps us understand the timing of spread of the virus, the subsequent aberrant growth, the virus' ability to hide through winter and to emerge with unexpected and unwanted vigor in Spring.

Rose Rosette remains a disease of aberrant and vigorous growth, to this add excessive and unexpected. We saw no "normal" growth emerging from the roots that spread thorugh the yard, but when RRD moved through the roots, each root made at least three new, sick plants. (These roots were ten to twenty feet long which is not the kind of growth we see with cultivated roses. Then, again, we won't be around to see our cultivated roses in their ninetieth years.) With 'Seven Sisters', there was growth over most of the rose, much of it new, much of it normal looking. Unfortunately for the rose, there were parts that were clearly aberrant. Now the bush is gone.

Several months after the bush and roots were removed, some of it came back up from small remaining root segments (May 19, 2001). Although they were only a few inches tall, the leaves showed a lot of veining (Fig. 1) that could be called vein banding and the growth from a root segment four feet away from the old bush shows the same type of growth as you would see from an infected cane (Fig. 2) a cluster of new stems where there should be just one. With an irony only ascribable to Mother Nature, this aberrant growth from left in place roots occurred after four weeks of drought.

We dug out additional infected growth from roots in the yard in the fall of 2001. Spring 2002, there is more growth emerging in the yard. This was an old rose with roots throughout the yard. The roots that remain are producing RRD-symptomed new growth, a year after the center of the rose was removed. We have removed five new growths from old roots this spring and two more have just emerged (May 2002).

Fig. 1 at left- Growth from a leaf that grew from a root segment. Note the discoloration, leaf veining, small deforned leaklets between large leaflets and powdery mildew.

Fig. 2 Above - A root of 'Seven Sisters' a few months after much of the bush was removed. The new growth looks like witches' broom from a cane.

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Part 3 - “We have a problem with our roses ....” by Ann Peck

The same October day we discovered RRD on our ‘Seven Sisters’, a consulting rosarian (CR) from another rose society called me with a list of symptoms that had her stumped. She wondered if the roses from the garden in question were suffering from rose mosaic virus. The symptoms reported to her included dense thorns, red stems and leaves and blooms that were not right. It definitely was not rose mosaic.

This CR had never seen rose rosette, nor was she familiar any of the kinds of rose mosaic virus, but I had told her about them some time earlier so she called me. She was faced with a problem described over the phone. I had seen so much rose rosette, that the time of year combined with those three symptoms were enough to know that these roses were prime candidates for a diagnosis as rose rosette. Larry and I arranged to go visit the garden the next day.

There were roses by the driveway with the symptoms above. We went in and a nice elderly couple started talking, even about the rose she had brought east from Nebraska, the family rose, pink and it bloomed all summer. Fortunately other family members still had the rose throughout the midwest, and this couple has two remaining plants. This garden had major problems with rose rosette in the same county where the first RRD-infected cane that visited my garden originated.

Six months later, the same CR called me again. This time it was in her garden - three plants. She recognized the problem - many people don’t. The assertion that RRD infects wild roses more than cultivated ones doesn't fit our observations. The feeling I get is that the percentage of cultivated roses infected may be much higher than the percentage of wild ones. There are so many wild roses - millions of them, that by raw numbers, you will have a large number of wild roses infected with RRD, but when RRD strikes a rose garden five to ten percent of the roses may be infected before the problem is diagnosed. Some gardens have lost an even higher percentage of their roses to this disease before any action is taken.

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