East of the Rockies? Check your nearby Knockouts

anntn6b(z6b TN)May 11, 2012

As massed plantings of Knockout roses beautify the landscape, the planters of masses of Knockouts too often plant them and then come back once or twice a year to prune them.

In some areas, these plantings can be a reservoir for Rose Rosette Disease.

For your own roses, you are going to need to keeep an eye out on the uncared for roses in your neighborhood to see if they remain healthy.

Today, I was out photographing Knockouts for a talk next weekend in Asheville NC (Arboreteum 10 am Saturday) and one planting that had looked ok a month ago now has two of seven KOs sick with RRD. Another planting had one of eight sick and across the road from it seven of seven sick. The latter two beds were at most two tenths of a mile from both Home Depot and Lowes where more Knockouts were being sold.

RRD on Knockouts stands out as different from normal good KO blooms, buds and leaves. It is a danger to roses down wind.

Take some time to read my e-book, multiple chapters and it has a FAQ.

Here is a link that might be useful: Rose Rosette E-book

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Wouldn't that be ironic? KnockOut's out-merchandize the majority of the rose market and then kill of the rest of the roses by serving as the reservoir for a fatal contagious disease? Who says the End of the World isn't in 2012?

    Bookmark   May 11, 2012 at 6:30PM
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stlgal(south z5)

Thanks for that post. The infection pressure in the St. Louis city limits is intense because of the density of these KO plantings. A couple of the major roadways (Kingshighway/Forest Pk Blvd) have KOs bulk planted in every median and the nearby buildings and even parking garages have them. You can walk around the central west end year by year as the disease worsens on the plants that have been present longer and then is acquired by new plantings within about a year or two or their having been planted. As I mentioned on a prior thread, the Missouri Botanical garden has removed their entire main rose garden and is unlikely to replant because they cannot afford the expense of replacing most of the plants every year or two.

I wish (but don't know of) any agency that could be convinced to deal with having these plants removed. I am thankful that the disease pressure out in the county is much lower and reduced still further as I patrol the neighborhood and root out any infected plants within range of my house gardens. I guess eventually there will be increasingly many areas where it will simply not be possible to grow roses because the external disease pressure is so high. So yes, I would say that it is not an exaggeration to say that there are some areas where the overuse of untended 'no care' landscape roses may ironically make it impossible to grow roses.

    Bookmark   May 11, 2012 at 7:03PM
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Please keep in mind that some/many/most? of mass plantings of Knock-Out type roses (particularily along roadways) may be subject to weed killer spray damage that is very similar to Rose Rosette Virus damage. The link below gives an article that appeared in an Iowa newspaper today.

It is possible that the mass plantings of Knock-Out type roses are serving a very valuable function - they may be the canaries that are warning us of:

"The medical evidence of harm regarding common household pesticide is sobering: Household and lawn weedkillers and insecticides use can increase risk of childhood leukemia as much as sevenfold; children born to parents exposed to pesticides have higher incidence of a range of neuro-developmental disorders; children living in households where pesticides are used suffer elevated rates of leukemia, brain cancer and soft tissue sarcoma.

The weight of evidence is overwhelming. Is a weed-free lawn worth it?"

The above quote is from the link below.

Here is a link that might be useful: Iowa View: Is having weed-free lawn worth it?

    Bookmark   May 11, 2012 at 8:27PM
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anntn6b(z6b TN)

In this instance you are terrifically misleading folks. The symptoms are so far beyond the 'classic' herbicide damage as to be intimidating.

Remember Herbicides kill plants.

Herbicide may stunt a roses' leaves. Herbicide doesn't spur multiple canes that are longer than the bushes extant canes. Herbicides don't cause a doubling or tripling of the number of buds in each spray, nor does herbicide cause buds to have a horrific overgrowth of sepals such that Audry II (from Little Ship of Horrors) looks like a first cousin.

Henry, your hypothesis may work some places. But if you were to see the ugliness that affects these roses in mass plantings, were to see the spread of RRD into potted roses for sale in garden centers (where they are freakin' unlikely to have been sprayed with herbicide), were to see the massive losses of productive bloom producers, were to see the fast growth of aberrant, excessive and unexpected growth, you would go to sleep, share the nightmares that many of us have, and worry about the future of roses.

Go to the library and look at the similar Emaraviruses, their vectors and the seriousness of their affects on food resources.

Nope, the problem in these parts isn't herbicide. Would that it were.

    Bookmark   May 11, 2012 at 8:58PM
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catsrose(VA 6)

I am beginning to suspect deer are a vector, that the mites are hitching rides. I know the wind can carry them goodly distances, but I am seeing RRD on hilly residential areas with no nearby multiflora sources but lots of deer. Several of my own that have developed RRD have been nibbled on, while the roses deer don't eat, rugosas and gallicas, are still clean.

    Bookmark   May 11, 2012 at 9:22PM
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The statement was made: "Remember Herbicides kill plants."

I suggest that for this discussion a more useful definition is: herbicide doses about a certain concentration will kill plants. For example low concentrations of Round-Up stimulate growth (see one example below). This type of effect is called hormesis.
Ann, I am not saying that RRV is not important. I am saying that both problems have to be recognized.

The University of Illinois presents a balanced picture (in my opinion):


My web information is at:


Here is a link that might be useful: Round-Up hormesis article with USDA author

    Bookmark   May 11, 2012 at 9:48PM
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stlgal(south z5)

I agree with Ann, it is very misleading to make a blanket attribution of these problems to herbicide damage when I can also attest that nearly all of the problem here is RRD. If there is herbicide damage it will be gone the next time the rose is trimmed. When these roses are shaped in spring, back comes the growth on the same affected canes. It spreads, as those canes get worse and worse, until they are as Ann described, true witches brooms of puffy ugliness, sending disease to the neighbors. The infected plants take years to die, during which they spread the disease to as many plants as are downwind. I've watched hundreds of new KOs put into different beds where I work over the past decade. At present, they have a year or two at most where the growth through the bed is clean--somewhere in that period, one or more always becomes diseased and then it is a matter of time while it spreads.

Here, over the past decade, one could follow the spread of the disease from bed to bed, down roadways and through mass plantings season after season. You become used to which canes on a particular plant have RRD, walking by the bush every day. The next spring it encompasses more of the plants you noticed the year before and is also visible on some younger plants put within a gentle breeze. With plants put in as these KO are, in mass groups of hundreds located in a close proximity, a steady spread of disease is inevitable and you can watch it happen if you watch the beds season after season, like I do.

Our Botanical garden is the pride of the area and for decades ran an awesome, huge rose garden. For them to decide that they simply cannot grow roses in the city of St. Louis because the disease pressures are too high tells me that Ann is not exaggerating in fearing that this disease is making it simply impossible to grow roses in some places. It is a threat to our continued enjoyment of these beauties and to the whole rose industry. Were that it were herbicide damage, indeed!

Even out here in the county I tolerate losses to RRD, but they are still tolerable. If, as in the city, they were much higher, I would also have to give up roses.

    Bookmark   May 11, 2012 at 10:21PM
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NOW I find this out! 120 knockout roses later...........

    Bookmark   May 11, 2012 at 10:34PM
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stlgal(south z5)

Just tend them and remove affected plants as needed--the problem isn't the KOs per se (they're no more likely than any other rose to get the disease). It is that commercial landscapers who want a 'no care' planting put in hundreds and walk away and there is no one to deal with the disease as it gets out of control. Plants can be sick for 5+ years before they die, during which they can spread infection to many other plants and these groups are all jammed together within easy spread of each other. So untended commercial plantings involving dozens or hundreds of plants are the major problem, because they are a huge, unremovable, festering source of RRD over years and years. No one is responsible for them, so you can't get them removed. If I had to live near the plants at my workplace, I wouldn't be able to grow roses. I fully understand why the public gardens are giving up, but it is a sad day when there is now no public garden where people can go to see and enjoy roses in our area. Maybe I should start offering my yard as a local attraction, since I probably have the largest Austin collection in the area.

Policing the neighborhood and woods for infected multiflora, KOs and other roses and educating the neighbors as needed is, by contrast, no problem. I do that within my area, which is why I can still grow roses here.

    Bookmark   May 11, 2012 at 10:51PM
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The following statement was made: "I agree with Ann, it is very misleading to make a blanket attribution of these problems to herbicide damage..."
H.Kuska comment. Please! Where is a blanket attribution being made?
The following statement was made: "If there is herbicide damage it will be gone the next time the rose is trimmed."
H.Kuska comment. Glyphosate in the soil enters through the roots. "Twenty months after the application the residues of glyphosate and AMPA in the topsoil (0�25 cm) corresponded to 19% and 48%, respectively, of the applied amount of glyphosate, and traces of glyphosate and AMPA residues were detected in deeper soil layers (below 35 cm). These results indicate rather long persistence for glyphosate in boreal soils."

    Bookmark   May 11, 2012 at 11:17PM
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Another very recent (May 11, 2012) article that attempts to present both possibilities.

"Distorted growth, witches' brooms and discoloration also can be caused by herbicide damage, so verify that no herbicides have been sprayed in the area. Herbicide damage, however, will not cause the prolific production of thorns you are observing on your roses."

Here is a link that might be useful: Chicago Tribune article

    Bookmark   May 12, 2012 at 12:13AM
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Sadly this reminds me of when I used to grow mainly fuschias.
Fuschia mite came and nothing except the most deadly of toxins would kill it. Even so, hummingbirds would reinfect the plants over again. Distorted leaves until the poor plant gave up. I had huge old plants that I trained into tree forms and giant displays on trellises. I had to drive by the neighbors sick plants 2 houses down every day or when I walked by. He would never believe me even though his plants were getting sicker all the time. Finally, I gave up on fuchias because I would not use the poison. I thought of containing them in a screened house but I couldn't afford it when I was a student.

It's a heartbreak for sure to see sick plants all around spreading plague. I passed out flyers about fuschia mite all over the neighborhood but my neighbor would never believe. Sometimes I wonder if glass houses aren't the way to foil mites and JBs or maybe a screened house surrounded by hedges. It breaks my heart to read about the large plantings of plagued roses. I have fuschias again now but they weren't like before and I never really got energized about it after the battle with mites took its toll on me.

    Bookmark   May 12, 2012 at 12:29AM
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2011 Award of Merit Article - American Rose Society.
"The Award of Merit Winners are outstanding articles featured in local rose society newsletters."

"Roses exhibiting symptoms of rose rosette may resemble plants that have been exposed to herbicides such as glyphosate (roundup) or 2, 4-D, or have a nutritional deficiency."


Dr. Raymond A. Cloyd is a Professor and Extension Specialist in Ornamental Entomology/Integrated Pest Management Department of Entomology at Kansas State
University, 123 Waters Hall, Manhattan, KS 66506

Here is a link that might be useful: 2011 Award of Merit Article - American Rose Society.

    Bookmark   May 12, 2012 at 12:39AM
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stlgal(south z5)

I wonder how many other cities have lost their public rose gardens to this scourge. Ann, do you know if we are unusual in that regard?

I saw my first case of RRD at the Botanical garden now about 6-7 years ago, and the loss of those rose gardens is one I feel personally. We typically visit several times a year (for more than a decade) and it was my only place to get a look at many kinds of roses in one place. I would go through the gardens checking out all of the fragrances and taking pictures of my favorites for later reference. Now the only place I can see roses is at Home Depot or the ones I see online and can mail order. It is truly a sad loss.

    Bookmark   May 12, 2012 at 9:21AM
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anntn6b(z6b TN)

The rose garden at Lincoln Memorial University is no more. Massive losses from RRD due to tolerance of RRD infected multiflora in an unkempt (and unsprayed) field immediately upwind led to lack of bloom.

The garden, which according to 'legend' was laid out to remind folks of Lincoln's face in profile as it appears on a penny, is gone, the hillside was regraded and the entrances to LMU changed.

Gage Park in Burlington Ontario, below their segment of the Niagara Escarpment, had a huge loss of roses. We only saw it when many, many had been removed. Of the remaining roses, a number of the Hybrid rugosas were covered with small witches' brooms and other distortions. I think they replanted it.

The corner of Brooklyn Botanical Garden (IIRC se corner of the area in back of their wooden structure has been replanted.

I know of some other gardens that had problems, but they didn't have the disease pressure.

Longest eradication was the removal of miles of infected multiflora along a river in southern Nebraska. Saddest was the eradication of three acres of roses in North Platte Nebraska that had comprised Glen Viemeyer's cold hardy breeding program. His asssisstant who still lives in North Platte remembers the day the roses were burned. Viemeyer searched for help in finding out what the problem was. Several well known rosarians told him it was herbicide. He fired back testy letters (I have copies of the correspondences) explaining that he knew what herbicide damage looked like as he had been one of the first people to work with that particular herbicide and what he was seeing in his roses was much, much worse.

    Bookmark   May 12, 2012 at 10:03AM
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buford(7 NE GA)

It's likely the density of the KOs and the fact that the ones in commercial areas and roadsides are just left with little or no maintenance beyond a clipping with a hedge clipper and pinestraw being put down once a year. So if the infected plants are not removed, it just serves as a carrier for the disease to spread into the other KOs and other garden roses. I'm going to start walking around my neighborhood and look at the KOs and other roses that may be diseased. I already found one next door (not a KO).

    Bookmark   May 12, 2012 at 11:11AM
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stlgal(south z5)

It's sad to hear that other places have lost their beautiful public gardens and plantings as well. A number of ironies here--first, as mentioned above, that the very 'no care' roses that have recently popularized the greater use of roses in mass plantings and landscaping are spreading a disease that ultimately makes it impossible to grow roses.

But perhaps another one that is a bit more positive--It is tough to educate the public (and landscapers) about a disease that was previously only an issue for the relatively small number of people growing roses. But as the mass planted KOs get RRD and sit in swathes of obviously diseased ugliness and slow death in public places they could serve as education about the disease, if we make use of them. It may take a decade or more before the downside of this KO planting craze becomes more broadly apparent to the landscapers and homeowners who have put them in. But possibly once that's common knowledge better practices can be encouraged. Our university's landscapers at least learned from past problems and put in beautiful mixed plantings in place of an embankment of massively infected roses. Having to remove a large number of diseased and dying New Dawns and other large roses must have gotten someone's attention sufficiently to get roses off of the next landscaper's plans. If enough people have that experience, maybe we can reverse this trend.

    Bookmark   May 12, 2012 at 11:35AM
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rosetom(7 Atl)

I hate Knockouts.

If RRD doesn't get them, BS will. Today's modern rose was just as disease-resistant 30-50 years ago. Seems to me that there are many "landscape" roses that BS affects greatly today that were supposedly disease-free just 10 years ago.

    Bookmark   May 12, 2012 at 11:45AM
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