P. Allen Smith's new rose garden at Moss Mountain Farm

Last week, when I was at the second annual Garden2Blog, I asked Allen if he’s seen any Rose Rosette Disease in Little Rock. He knew immediately what I was talking about, and he said he hadn’t seen “witch’s broom,” the more common name for what is currently being classified as a rose virus. As we sat in Allen’s new and exquisite rose garden, I thought . . . No, I hoped RRD wouldn’t touch his peaceful valley dedicated to Lady Elizabeth Ashbrook, his friend and mentor. One of the reasons I attended Garden2Blog this year was to see the new rose garden at Moss Mountain Farm. Bloggers saw plans last spring, but now the garden is a reality. I love to see things come to fruition.

Rose bed at Moss Mountain Farm. It's a new garden, but one day, those roses will climb up into the tuteurs.

Steve Hutton, President of The Conard-Pyle Company, which distributes the Knockout® family of roses and many other roses including the Romantica® Collection, Star® Roses and Drift® roses in the U.S., talked to us about new, disease-resistant cultivars, the star of which is Francis Meilland™,  the 2013 AARS winner. I’m testing two Star® roses in my garden this summer, ‘Meikanaro’ a/k/a Sunshine Daydream, the 2012 AARS winner, and another cultivar I’ve yet to identify–as it came without a tag. As Steve talked, all I could think about was Rose Rosette, and how it is spreading rapid-fire throughout central Oklahoma. After he finished, I asked him his thoughts about RRD. I was encouraged that Conard-Pyle is well aware of the problem. In fact, their company is funding research through the University of Arkansas. Here is their statement which they sent me when I emailed them after I returned home from Arkansas:

“Conard-Pyle is working with Dr. Ioannis E. Tzanetakis at the University of Arkansas.  Conard-Pyle is really committed to combatting RRD, and continues to aggressively fund and coordinate research on many different levels with many industry professionals.”

You may not know, but in Edmond, Oklahoma, where the original Knockouts® have been planted anywhere there was room, Rose Rosette flourishes, and it seems attracted to the Knockouts®. Perhaps, it is because they are planted so close together so that RRD spreads more easily. It could also be because Knockouts® grow so quickly, and the virus simply shows up in them first. In Edmond, I’ve only seen it on the original red so far. I find it odd that the original Knockouts® are being hit so hard in the city because, thus far, none of my Knockouts® indicate the disease. I grow the original Knockout®, Rainbow Knockout®, Double Knockout®, single Pink Knockout®, Blushing Knockout® and ‘Radsun’ a/k/a Carefree Sunshine. I also grow the later introductions: Home Run® and Winner’s Circle®. These roses are the backbone of my disease-resistant garden, and I would be sad to lose them.

To identify RRD, look for large, tender shoots showing unusual thorns and foliage that looks sickly and broom-like such as this below. By the time you see the “witch’s broom,” the disease is well on its way to killing your rose.

Rose Rosette Disease on my 'Zephirine Drouhin' rose. Note the sickly pinkish color, and the misshapen roses behind the "witch's broom."

In 2010, I lost one ‘Zephirine Drouhin’, an ‘Old Blush’ shrub, and two ‘New Dawn’ climbers to this scourge. Because current literature states there is no cure, I dug all four roses and disposed of them in plastic bags in a dumpster at our company, far, far away from anyone’s roses. Landscapers need to take this problem seriously and dig up effected roses immediately and plant something else in their place. Wingless, microscopic Eriophyid mites carried on air currents spread the disease from plant to plant.

To combat the disease, space roses far enough apart to keep these non-flying mites from spreading the virus. I also grow my roses as shrubs with other plants. I hope this helps retard the disease’s progress in my garden. Note that chemicals have limited success on Eriophyid mites. I don’t use chemicals, but the Virginia Extension Service indicates what does work if you want to go the chemical route. Miticides for spider mites apparently do not work.

From the Virginia Cooperative Extension (emphasis added):

“Some symptoms, such as leaf coloration, may be subtle. Although some diseased plants develop very obvious red pigmentation, others exhibit a less striking reddish pink color on leaf undersides or along the margins of otherwise green leaves. Since the new leaves of many rose cultivars normally have reddish pigments, it may be difficult to determine whether the reddish color is abnormal or not. Therefore, it is important to continue to monitor symptoms on suspect roses. On RRD-infected plants, the reddish color does not go away, whereas on healthy plants, the reddish color usually disappears as the leaf matures. Witches’ brooms on some diseased plants may be an unusual color of green that can be mistaken for symptoms of a nutrient deficiency. However, nutrient deficiency should affect the whole plant. If these symptoms appear only on parts of the plant, they are probably not due to nutrient deficiency, and RRD is more likely.”

The people from Conard-Pyle stated that any rose with Rosa chinensis in its background was susceptible to the virus. This news especially saddened me because R. chinensis is in almost every modern rose. It is what makes roses remontant, or reblooming.

I am concerned for anyone in Edmond who grows roses. If you see roses with RRD, consult the local authorities and refer them to online sources about the disease. Roses with RRD must be destroyed, but not composted. Also, because any roots retain the virus, you cannot plant roses in the same spot unless you dig two feet of soil from the area where the roses were and remove all of the roots. Do you know hard it is to completely remove rose roots? I still get shoots of ‘New Dawn’ now and then. I dig and destroy them.

This is a very serious problem. I’m grateful that Conard-Pyle is trying desperately to solve it. It saddens me to think I might one day have a garden without the scent of roses, but I’m willing to destroy every plant to halt this plague if I must. I hope it won’t come to that.

Note: As with all of those who attended Garden2Blog 2012, I received transportation, accommodations and meals during the event. I did come one day early and pay for my own hotel room. Event sponsors, like Conard-Pyle provided information, samples and product giveaways at no cost or obligation. Before I attended Garden2Blog, Conard-Pyle sent me two roses to test in my garden at no charge. All of the other roses mentioned in this blog piece like the Knockouts® I grow I paid for with my own money. I’ve grown Knockouts® since they arrived on the scene years ago, and I love their carefree ways.