The consequence of repeated defoliation on roses that are susceptible to blackspot is this ... the leaves are the food factories for the rose. If the rose has to continually refoliate itself, whether from blackspot or another reason, it uses precious stores of carbohydrates to do so. This can eventually cause it to wither away and die. This is a generalization, and it's not always the case.

This is also why the roses that we find that have survived for a long time in cemeteries and at abandoned homesites are such treasures. They are probably not the only roses to have been planted in those locations over the years ... but they are the ones best suited to the conditions because they survived.

As hartwood stated, severe, repeated cases of black spot over a long period of time can eventually kill a rose. Not of itself but by robbing it of the energy that it needs to continue to grow.

In your case a very severe case in the fall, going into winter, could sap a rose of the energy it needs to come back in the spring. If it's still warm enough for the rose to grow it will try and produce new leaves using up the energy it has. That new growth has no hope of wintering over and so in the spring the rose has no energy stored to produce new leaves to replenish it's stores with. It's one of those vicious circle things.

Ok. That is good information. So essentially there is nothing I can do about it right now? Also, next year, should I go ahead and assume that rose will blackspot and begin preventative with Cornell or manure tea?
Thanks.
Susan

How you decide to deal with it is your own choice. However, either removing the bad actors or spraying with a modern fungicide are the real choices. Cornell or manure tea have about as much affect as backyard naked dances.

In my experience blackspot does not hurt roses. They drop their leaves, then grow new leaves at their own pace; they do fine. Blackspot does not diminish vigor or hardiness.

I think that roses have natural strengths that enable them to defend themselves against blackspot. I've found that organic fertilizers and topdressings create an environment where roses thrive, even with blackspot present in the garden.

Regarding krista's comments. I have posted this information (or something similar) many times on the web:

"There is a another choice. This choice is to allow the friendly fungi to reach equilibrium with the blackspot. This choice comes under the heading of "biocontrol".

The following may be useful in putting the concept of biocontrol into layman terms:

"Disease-suppressive soil microorganisms have been found in many places. In monoculture wheat the severity of "take all" disease often decreases within three to five years. This phenomenon is known as "take all decline," and is considered an effective natural control. Although the mechanisms are not completely understood, the decline is associated with changes in soil microorganisms that compete with and prey on the fungus. Melon plants grown in the Chateaurenard region of France do not show Fusarium wilt symptoms even though the fungus is present in the soil. Soils with suppressive characteristics tend to develop slowly and are usually found in fields where perennial crops or monocultures have been grown for many years.
Suppressiveness may be lost if the monoculture is interrupted even for one year, or if pesticides are applied. For example, researchers first recognized soils suppressive to cereal-cyst nematode when nematode numbers increased after application of a broad-spectrum biocide. Many species of fungi and bacteria in the genera Trichoderma, Streptomyces, Bacillus and Pseudomonas suppress diseases, but at this time only a few strains are commercially available. Additional commercial products may be available soon, however, as this is currently an active research area."

The quote was taken from (link no longer works):

http://www.cals.ncsu.edu/sustainable/peet/IPM/diseases/org_cert.html

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A scientific study (2007) of biocontrol of blackspot of roses:

http://www.tandfonline.com/doi/abs/10.1080/17429140701701071

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Thread where the above appeared:

http://forums2.gardenweb.com/forums/load/rosesant/msg06130420825.html

In the final analysis, I believe firmly that if a plant is that sickly where you garden, you are probably wisest to shovel prune it, and replace it with something that's happy to grow there.

That said, Henry's suggestion isn't a bad one.

During one of the earlier outbreaks, here, of downy mildew, we found the various drenches pretty ineffective. And when the stuff melted a plastic measuring spoon, that was -- THE END of that.

Injecting beneficial organisms was a new idea, but before we tried that, we listened to local avocado growers, who were dealing with a closely-related fungal agent, which caused "Avocado Root Rot."

Because a LOT of money was at stake, a lot of serious research went on. They eventually abandoned all of the chemical drenches, and moved, instead, to mulching around the trees, out to the drip line, with all the fresh horse manure they could get ahold of. We took the same steps.

And darned if it didn't work!

That organism cannot be killed. But it can be supressed. And the trees (and the roses) benefitted from a healthy bacterial colony, which effectively supressed the bad fungus.

All that said, if I had a rose so badly affected by fungal disease that it was dying -- I would choose not to grow that rose.

Jeri

Ok. So top dressing of fresh manure. But fresh manure will burn roots, so it doesn't go in the hole or get worked in right? Rotted manure goes to the roots?
I can't tell if my rose is dying or not? It's defoliating like crazy but also sending out new growth and blooms...
So, will I know it's dead in the spring? Well duh...I guess I will know it's dead. Ha
So, having analyzed opinions here I've come to the conclusions that 1. organic control (manure tea etc)of blackspot doesn't work on foliage. Well, assuming that backyard naked dances don't work!
2. fresh manure as a top dressing helps to control fungal disease
3. if a rose has defoliated 90% by the end of summer it should be SP'd
I love learning from you all.
Thanks.
Susan

Susan, what rose is it? is it in a pot still or in the ground?

Susan, I should clarify my comment... my roses defoliate, however this is routine and in my humble opinion does not hurt them.

So when I use the word thrive, I think of them as strong garden plants, even with total defoliation... they come back beautifully in the spring time, and I get repeat blooming in cycles in summer and autumn.

90 % defoliation is typical for my roses, only a humble opinion, but I would not recommend shovel pruning a rose when this happens...

Will it kill a rose? Maybe, but really it is best viewed as a symptom of other ills; a stressed rose because of lack of sun, air movememnt, poor soil, etc.

Another consideration. I live in an area where blackspot isn't a problem: probably because of our dry summers my roses simply don't get it, at least not during spring and summer. However, at the end of the growing season, when days are short and cool and the air is humid, quite a few of my roses get some blackspot shortly before they drop their leaves. Is the blackspot on your roses an end of the season phenomenon? If so I wouldn't worry about that.

I wonder if end of the season blackspot isn't part of Nature's way of preparing roses for winter.

Blackspot certainly can kill roses, some roses.

My climate has maximum blackspot pressure. There is an old public rose garden here that was sprayed by a neighborhood volunteer for a while and then not sprayed. The roses (I recall only 'Red Masterpiece,' 'Charlotte Armstrong,' and 'Crimson Glory') died out around 1982 and were replanted with mostly hybrid teas. These died out except for 'Chrysler Imperial' and 'Topaz Jewel.' Then it was replanted with a melange of kinds including Buck roses and some Austins, HMsk, and others. The varieties that died out included plantings of 'Our Lady of Guadelupe,' 'Fair Bianca,' 'Fabulous!' 'Prairie Valor,' 'Sun Flare,' and 'Yves Piaget' (whole groups not individual plants). However, many other roses have survived for over a decade, and some of these periodically defoliate from black spot. The survivors tend to be the more vigorous or more winter-hardy varieties. These include 'Country Dancer,' 'Winter Sunset,' 'Teasing Georgia,' 'Traviata,' 'Penelope,' 'Carefree Delight,' 'The McCartney,' and 'Mozart.'

Oh, 'Fisherman's Friend' is a winter-hardy variety that died out from its extreme susceptibility to blackspot--it could hardly mature any leaves before they sickened.

Those plants that were grafted were planted deep enough that, had they been sprayed, they should have survived. In my personal garden I have had zero winter losses since 1984, with no protection except buried grafts.

So in that public garden I have personally seen hundreds of roses essentially killed by blackspot, that is, debilitated by repeated defoliation to the point they did not survive winter. (The first generation of plants were exposed to some severe winters, but we have not had subzero temperatures for 25 years. The third generation certainly has not faced zero.

Michael

A rose bush that's bare naked except for a fluff of fresh foliage and buds at the end of the canes is ugly. Just plain ugly. I wouldn't tolerate any plant that looked that bad in my garden. My roses are antiques and they stay at least 80% foliated all summer or they get replaced with another rose that will. Your mileage may vary.

Susan - a few responses to your post, but please understand I have no experience in your particular zone.

Ok. So top dressing of fresh manure. But fresh manure will burn roots, so it doesn't go in the hole or get worked in right? Rotted manure goes to the roots? Correct. Fresh manure above ground and not touching your canes. Well composted manure can go anywhere.

I can't tell if my rose is dying or not? It's defoliating like crazy but also sending out new growth and blooms...
This almost sounds like your rose suffered a sudden traumatic condition - like completely drying out, or some other stressor. New growth and blooms means - don't grab that shovel yet.
So, having analyzed opinions here I've come to the conclusions that 1. organic control (manure tea etc)of blackspot doesn't work on foliage. Well, assuming that backyard naked dances don't work! While backyard naked dances won't help blackspot, they could have interesting effects on the neighbors

2. fresh manure as a top dressing helps to control fungal disease
3. if a rose has defoliated 90% by the end of summer it should be SP'd There is no, hard fast rule here. Part has to be "gut" - is my rose improving, deterioriating. What are the surrounding conditions causing issues with my rose (like, is it completely crowded out, or in full shade and should just be moved)?
I love learning from you all.
Thanks.
Susan

Another variable with roses dying is virus infection. Many/most/? of the roses sold had virus infections. In colder climates the rose immune system is not effective against the most common classic virus, PNRSV, and it was my experience (and reading) that it was not uncommon to find that virused roses in northern gardens were more likely to die from winter stresses. I would not be surprised that season long blackspot stress would have a similar effect to winter stress on virused roses.

In our experience, using fresh manure was very successful in our coastal Southern California conditions.

When I was told that, I was doubtful.
Experience has told us that it works fine.
It has never burned roots here.

I would not pile it right up against the canes, but here, roses LOVE fresh horse manure.

Jeri

Thanks to everyone for taking the time to offer your experience. The rose is a climbing Peace, about 3 years old. It's in a hot spot. Likely got dry and not as well fed as mine in pots. I've only had end of season blackspot here and yes, it may be a way to defoliate for winter. Most of my roses are spotting a bit here and there--the Austins aren't.
I will give this one more TLC next year but she is in a hot spot 2 ft from a dark brick southern exposure wall.
Susan

Even if it doesn't outright kill a rose, it can compromise the plant and prevent blooming. And why do we grow roses? Is a spindly leafless plant with one bloom on it what we want?

I have roses that never bloomed with any regularity until they were spray. They could just never generate enough energy. So you choose if you want to spray or not and add roses accordingly.

The reason we gave up on trying to grow 'Peace' here in La La Land was that she was subject to every disease that came along.

The reason we gave up on trying to grow 'Cl. Peace' here was that it was subject to every disease to come along, AND didn't bloom.

:-)

Jeri

I agree with Henry's research data that showed a healthy balance of flora is essential to suppress fungal growth. I checked the species that Henry listed: Trichoderma, Streptomyces, Bacillus and Pseudomonas. Trichoderma is the fungus growth in corn meal which suppress mildew even better than blackspot. Bacillus and pseudomonas are the bacteria in animal manure.

I also agree with Henry's thought that "Blackspot is a natural process, end-of-bloom cycle". Potassium is needed to fight diseases and strengthen stems. Potassium is needed for bloom production as well. At the end of a blooming cycle, the potassium is deleted, hence decreased resistance to fungal disease.

Per University of Kentucky's data on Organic Fertilizers and Composts for Vegetable Transplants: Potassium in cow manure is 191.7 ppm, in composted worm casting is 1,751 ppm, in horse manure is 3,476 ppm - compared that to 82.6 ppm in MetroMix 560.

Earthco. that tested my soil reported that 1/3 soil tested are deficient in potassium. Depletion of potassium is more evident in 3rd year, when the rose bush becomes too large for sufficient uptake of potassium. The use of fertilizer high in salt index also drives down potassium. Most nitrogen fertilizer have a salt index over 74, except for anhydrous ammonia at 47. Chemical fertilizer is best in spring time, when there's sufficient water to flush it down.

As to large scale testing of the effect of potassium in conjunction with lime, below is the link of test data on soy production, which showed the largest yield in crop with lime pellets and sulphate of potash, which beat using fungicides alone. Lime is a natural fungicide. I'm next to a lime stone quarry. I was walking and checked my neighbors' roses - all are clean like mine. They planted Angel Face, Rock n' Roll Grandiflora ... their HTs are clean like my 2nd year Golden Celebration below, its base taken this fall.

However, the library's hedge of Lady Elsie May, only 5 minutes from me, are naked with blackspots since early fall. I broke out laughing when I saw a guy there with a HUGE chemical canister, was spraying a tiny dandelion. He could had easily reached down and pulled it up.

{{!gwi}}

Here is a link that might be useful: Report on best yield through sulphate of potash and lime pellets

Thanks, Strawberry and Henry for the chemical explanations. I think I understand. What I took from your posting would be that horse manure is the best manure for top dressing to prevent fungal infection and that lime and potash are excellent top dressings to put in place at the end of a bloom cycle?
Did I get that right?
Thanks
Susan

I'm getting ready to dig out a climbing rose that's been in my garden for at least ten years, totally blighted with blackspot. On the one hand, it's still alive, and seems a little bigger each year. But it spends most of its season each year all but denuded of leaves. Desperately pushes out more leaves, just to lose them again. It's a miserable-looking specimen for about 49 weeks of every year. Only my ignorance of roses, and more general lack of priority for the garden over the past decade, including several years of total neglect due to babies, renovations, etc., has kept me from replacing it sooner. But more to the point of your question: the rose has not died on its own.

For what it's worth: As a horse person that does a little gardening I would tell you that I know several people who throw steaming fresh from the horse manure on plants and have zero problems with burn. I haven't tried it myself, but considering my abundant supply of manure as well as plants I may need to experiment with this next spring!

subk3...fresh from the horse manure works here in the fall. I think the rain dilutes it's acidic properties..
Jeannie

Yes, repeated defoliation from blackspot can weaken a rose bush and it will die over the winter if it doesn't have enough energy reserves to bounce back in spring. It depends on the vigor of the rose variety and how much/how quickly it defoliates. If it looks really bare-legged, spindly and poor in the garden you might want a healthier variety anyway, even if it survives. Though I've kept some suseptible varieties around because of wonderful flowers and fragrance, I try to choose varieties that have more built-in resistance and replace the worse ones.

What Lori said: repeated, severe infection of Diplocarpon rosae will weaken many cultivars to the point that winter stressors will kill the plant. It is not the disease itself, but the unrelenting erosion of the plant's defenses and depletion of its resources that brings about its demise.

"the library's hedge of Lady Elsie May, only 5 minutes from me, are naked with blackspots since early fall."

Selection of regionally clean cultivars doesn't get enough attention.

I really though Lady Elsie May was a healthy rose, because when I saw a mass planting in Orangeburg SC in late fall, not a leaf had dropped and they were covered with blooms.

Wow, what a difference.

Since I'm in a cold zone 5a, soil suitablity is more of a factor in winter survival than BS. Someone in acidic east coast mentioned that Rugosa is among her healthiest. It's the opposite in my alkaline soil, pH 7.7. OWN-ROOT Austin Eglantyne has Rugosa heritage, hates my alkaline soil, and lost all leaves to BS, compared to my 100% healthy Romanticas, not a trace of BS. Romanticas are bred in France with higher pH.

I lost own-root Eglantyne last winter. I planted another own-root gallon-size, and watched its roots shrank in my alkaline soil. When the pH is not suitable, the roots can't absorb the potassiumm needed for bloom and to fight diseases. Eglantyne gave me 2 blooms, versus Romantica Liv Tyler gave me 40+ blooms for the year. Eglantyne has the worst blackspot, versus 100% clean Liv Tyler. My own-root Golden Celebration and Evelyb are also 100% clean, both are known to thrive in alkaline soil.
t

"Austin Eglantyne has Rugosa heritage, hates my alkaline soil, and lost all leaves to BS"

While 'Eglantyne' does have Rugosa genes in its pedigree, they are sufficiently far back in its breeding line to be of no value whatsoever, as far as health of the hybrid is concerned. In fact, it is well-known among hybridizers that most first generation hybrids made with R. rugosa (when crossed with modern remontants) have little or none of the health of that species.

Trospero, you are right that most hybrids made with R. Rugosa don't resemble Rugosa IF THEY ARE GRAFTED ON DR. HUEY, which thrives in alkaline soil. Krista in New York has Eglantyne grafted on Dr. Huey, it has 80+ blooms per flush, versus MINE OWN-ROOT at 2 blooms per year. Krista notified me of Eglantyne close resemblance to Conrad Ferdinand Meyer Rugosa at NY rose park.

Kim Rupert crossed a very healthy My Stars with MORrosrug (rugosa) and got a diseased-ridde seelding that he killed. It didn't do well in his alkaline soil. Take Jude the Obscure with Peretiana Soeur Theresa in its lineage. Peretiana likes it dry and hot. Jude the Obscure grafted on Dr. Huey is over 6 feet at the park, blooms well. Jude the Obscure OWN-ROOT bears more resemblance to its parentage, hates rainy weather, breaks out in BS, and is stingy on folks, like 3 blooms per year.

A rose can be made more suitable for alkaline clay if it's grafted on Dr. Huey. As own-root, it will show its true colors to its heritage.

"Kim Rupert crossed a very healthy My Stars with MORrosrug (rugosa) and got a diseased-ridde seelding that he killed. It didn't do well in his alkaline soil."

It probably wouldn't have done well anywhere, since 99.5% of all roses raised from seed are flawed in one way or another, especially in regards to their health. So, it is important to bear in mind that one seedling is just that; a single data point, and it is unwise to draw conclusions based on a single data point. It is the other 99 seedlings from the same cross that tell us something about the merit of the mating.

'My Stars', in complete contradiction to its pedigree (the dreadful 'Playboy' was a parent) is capable of producing some remarkably healthy, vigorous offspring. As I said, crosses of Modern X Rugosa often yields a vast number of unhealthy, troubled offspring. Ralph Moore likely grew several hundred seedlings to obtain 'Linda Campbell'!

I raised that seedling out of curiosity. Paul is very likely right, it probably wouldn't have done well anywhere, which is why I shredded it. The results answered my "what if?" appropriately. It is also valid to remember that lone seedling was the BEST of the lot, and it wasn't very good at all. The flower was pretty and it was large and fragrant. Otherwise, becoming part of the shredded mulch was its highest valued use.

Mr. Moore raised thousands of Rugosa hybrid seedlings over his many years, and 99.99% of them were garbage. Sheer, unadulterated garbage. Most refused to flower AT ALL, even after growing them on for many years. Most were rangy, thorny and horribly disease prone. While he succeeded in raising a few which, in the right climates, are pretty good garden roses, if his dinner every night depended upon that breeding line, he and his family would have starved many years ago. Kim

Thank you, trospero, for that very interesting info., I appreciate your knowledge. It's only my hunch, so I need your experience on this, trospero, regarding my own-root roses:

1) Meilland in France, a more alkaline soil with hotter summer, bred roses vigorous as own-root in alkaline soil. David Austin, in more acidic soil and cooler climate, bred roses more vigorous as own-roots in such environment. Nahema with Heritage as the parent is wimpy here, only 5 blooms per year. I dug up Nahema and the root is very small. In contrast, Meilland Liv Tyler produces tons of blooms and the bush is 3 times larger in my hot summer near 100 degrees.

2) Kim Rupert bred "Annie L. McDowell" by choosing the best seedling of Renae x Renae in his alkaline soil and water. I bought Annie as a tiny band, now its rootball is huge, at least 2 gallons when I transferred from pot to soil yesterday. Compare that to Nahema with Austin Heritage as pollen parent, bought as gallon-size, but its root shrank here.

My conclusion: buy own-roots where it's bred in a climate and soil similar to one's own.

Austin's Eglantyne was reasonably disease-free here, but it was so boring DH kept forgetting it was there.

Jeri

Thank you, Jeri, for that info. Was your Eglantyne grafted on Dr. Huey? The breeder Robert Neil Rippetoe informed me that his Eglantyne grafted on Dr. Huey does really well in his hot climate and alkaline sandy soil.

Rugosa rose is known as "beach rose" due to its drought-tolerance and doing well in sandy soil. OWN-ROOT Eglantyne with Rugosa parentage can't push through my heavy clay, to extract potassium for blooms and to fight diseases. Thus it's the type of soil and whether it's grafted, rather than the pH that matters with Rugosa. I checked with another grower in Connecticut ... his Eglantyne is own-root in acidic soil, and also very stingy.

The rose park 15 minutes away used to grow Rugosas - they were stingy-bloomers in our alkaline clay - and I'm so happy they got rid of them.

No. I think pH matters a great deal with rugosas. Soil type may be an issue, but pH matters too.

I love rugosas, but they are miserably unhappy here, so there is no point in growing them. (We are coastal, btw, and our soil is more or less sandy.)

Anyhow, our Eglantyne was budded, but whether on Huey or Multiflora, I don't recall. It's a good many years since its roots went to the kindling pile. It did bloom relatively well, but . . .

Jeri