"Is BS a real concern? Is it really harmful to the rose, or simply unsightly? "

Blackspot has the ability to severely degrade a rose if left untreated. In colder climates like yours, it can weaken a plant in fairly short order and leave it susceptible to death by freezing in the Winter. In warmer climates, it can be less of a problem in that the climate allows plants to hobble along and recover between bouts of disease. Mild cases of the disease can be little more than a cosmetic nuisance, or if your climate favors the disease it can be devastating and must be dealt with either with Fungicides or elimination of susceptible varieties and replacement with those that do not get the disease.

My experience in my 1000 rose, zone 5, inland, northern Ohio, rose garden is that after about 5 years of no-spray that the blackspot problem takes care of itself (an equilibrium of good bugs - bad bugs has been reached). Of course this does not help the exhibitor who must have perfect leaves and may not apply in much more humid climates.

It also depends on a rose. Some roses can loose all their leaves, and stay naked all summer, but still keep going. They Look ugly, but it is not detrimental. There are other roses that get weak with even 50% leaf loss, gradually decline and don't survive winter. I certainly saw many roses that were killed by BS, so it is not just cosmetic.
As already mentioned there are two approaches really. First, to grow resistant or at least more resistant roses (and there are some for each climate). Second, spray fungicide on a regular schedule. I don't think it is possible to grow Double Delight here no spray, but your climate can be better. You always can just try and see how it works for you.
Olga

Ditto.

But I'm not sure what henry means by good bugs. Is there a good fungus that eats up blackspot? Can I cook it up on the stove or grow it in the fridge? That would be awesome.

I'd love to know the answer to the blackspot question myself. It comes and goes. There seem to be a million variables affecting it, so it's hard to tell what works and what doesn't.

'Francis Dubreuil' defoliated early last season, but regrew it's leaves and stayed nearly clean the rest of the year. That surprised me.

'Souvenir de la Malmaison' went through a slow but constant cycle of shedding and regrowing leaves all year. I resorted to organic spraying to slow the blackspot down. In my opinion it helped, but see below.

'Blush Noisette.' Very strange with this one. I noticed the tell-tale spots one day. Very disappointing since this was a variety recommended for my climate. But the spots didn't get larger. Really looked like the plant had sort of contained the infection. Then it bloomed, and the blackspot took over and it defoliated.

I've read similar testimonies on the web: the rose is fine until it blooms, then comes the blackspot. Does the effort of blooming weaken the plant and make it more susceptible to the disease? Would giving it more fertilizer when in bud help it to resist it?

I was using Neem oil as my organic fungicide, but now I'm reading that may be a problem to bees. So that may be out.

I do wish someone would find the earth friendly cure for this one. If I ever give up on roses, you can be sure blackspot was the reason.

See:

http://www.informaworld.com/smpp/content~content=a783868824~db=all

I was able to get the full paper. Probably the most interesting item is their Figure 9 which gives the results they obtained 75 days after spraying the rose "Edward". The no spray control had a "percent disease index of about 65, the chemical spray control (using Tridemorph) had a disease index of about 35, Pseudomonas fluoresens treatment had a disease index of about 45 and Trichoderma viride treatment had a disease index of about 40.

Here is a link that might be useful: Recent scientific paper

Is there a good fungus that eats up blackspot?

*** Well, there's Serenade -- not a fungus, but a bacterium.
Only, it's not easy to find.

Jeri

Hmmm. So if I'm reading all of this right, BS is not so much to be *feared*, as *managed*. Am I right? I'm starting to regret giving up DD...I wouldn't have minded spraying her in order to keep her heavenly blooms and fragrance. Too bad. I have often heard that allowing your rose leaves to get wet during a night watering contributes to BS and have tried to obey the rule, but it's almost impossible to water without getting the leaves wet (or am I doing something wrong?), and I noticed that my mother-in-law waters with careless abandon at night and never has a problem at all.

So, as far as spray goes, what to use? If neem oil is bad for bees, what about the Bayer stuff? I read on another forum that someone also experienced a remission from BS after 5 years. Is it some sort of magical time lapse? Has anyone else experienced this?

The after 5 year "remission" was probably due to what is termed "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:

Http://www.cals.ncsu.edu/sustainable/peet/IPM/diseases/org_cert.html
----------------------------------------------
The following article from the Maine Rose Society web page ( http://www.mainerosesociety.com/articles/control.html ) was written by by DR. LAKSHMI SRIDHARAN, who should be familar with those of you that are members of the American Rose Society.

Here is a link that might be useful: Maine Rose Society article

So what is the latest theory on overhead watering and BS?

Since we have had no appreciable rainfall since October, I have been watering with sprinklers all winter and spring. No disease yet, but it may be too early. I have a no-spray garden and the foliage is the best I have ever seen it for this time of year.

I climates where BS is bad, it really doesn't matter. Overhead or not you will get BS on most roses except most resistant if you don't spray. Leaves will be wet at night because of dew anyway.
Olga

Maybe it's my climate or maybe it's the roses I've grown, but I've never seen blackspot "weaken" a rose in my garden, even for roses I've grown that are susceptible to the fungus.
Ugly for sure, but not "weakened".
Perhaps, as mentioned above, it's my relatively warm zone 8 that keeps blackspot-prone roses from being damaged during winter.
Take 'Paul Neyron' for example.
Very blackspot-prone in my garden.
Defoliates often during the year.
Always comes roaring back each spring as if nothing happened.

Randy

Randy-- yes, roses that are fully cane-hardy in a particular climate are likely to survive after repeated defoliation. But in my climate and colder, some roses have to be pruned to the ground in spring and completely regrown over the season. This puts a high demand on energy stored in the crown and roots.

greybird-- it's proven that overhead watering reduces blackspot and powdery mildew. For blackspot control, the water must dry 100% before nightfall. For mildew in climates where blackspot rarely occurs (coastal southern California), midnight watering is beneficial.

bellegallica-- salad oil or commercial spray oil (refined mineral oil) would probably be as effective as neem oil with no risk to bees. However, most neem oil products have had the insecticidal ingredient (azadirachtin) removed anyway. I would not worry unless the product is labeled "whole neem oil." I have extensive experience with micronized sulfur as a fungicide. It has been more effective for me than other organic remedies. It is safe for animals and insects, but can burn plants in hot weather, esp. if water is scant.

Regarding roses surviving blackspot. Some/much/most/all? of the older experience with the dying of blackspot stricken roses may have been based on roses weakened with rose viruses, and/or roses forced into excessive growth by extensive use of heavy nitrogen based fertilizers, and/or roses grown on "dead" soil due to the extensive use of fungicide sprays, and/or roses that were born weak (but since they had pretty flowers, they were introduced anyway). It is my understanding that normally nature reaches equilibrium between preditors and prey (lions generally cannot catch all zebras, only the old, young, and/or sick). In other words I would expect that healthy roses will normally be able to survive blackspot attacks.

In the past I have stated on this forum that I do not worry about late fall blackspot as I assume that the resultant leaf drop is part of nature's plan to shut down the roses for winter.

Perhaps it would be useful to think about what the leaves are there for-not as ornaments but as food factorys. If your plant stores enough food then it will survive the lose of its leaves -if it doesnt it wont, and everything in between. Flowering takes a lot of carbs out of a rose bush so it makes sense that disease prone roses will have more problems after a flush. Perhaps once bloomers are often more disease resistant because they can spend most of the growing season storing food?

patricia

There is a disconnect between the scientific papers and what gets reported from the real world.
Even the American Rose Society only asks about black spot and probably (ok, inevitably) gets reports on Black Spot, Cercospora, Anthracnose and Downey Mildew in the mix. Likewise, people will report great results with a fungicide and not realize that the real solution was the increase or decrease in temperatures (such that the fungi are no longer in their optimal growth range as so their roses are 'cured' when the disease is just supressed until the next copacetic temperatures intercept the fungal spores and roses.)

I think the best info is going to be local, and it will come from people who have tried a lot of things and found what works. But the only way that this can work is if we are extremely careful of the diseases we bring into our gardens. The count of the number of strains of Black Spot and Powdery Mildew seems to conintue to grow. We don't know which respond to which fungicides.

My answer, in my garden, is intollerance of roses that can't be cured of classic Black Spot. Sick roses share their problems.

Sorry for going somewhat off topic, but it's hard to compare Fungi and Fungi when we aren't even sure we're talking about the same thing.

Ann in Tennessee has nailed it, IMO.

I have some blackspot and I usually don't do anything about it. I don't live in a very heavy blackspot climate so there should be plenty of roses that will do fine with no blackspot treatment. I'll slowly find them. It's not a death sentence most of the time.

I don't exhibit and I don't need picture perfect gardens. I do enough fighting with nature in keeping blackberry proliferation at bay.

-Greta

Wow. Now I'm really confused. Black spot and powdery mildew are the same thing? From the same family perhaps? What about just removing the infected leaves as you see them appearing? Will that keep the BS or the PM from spreading?

You picked up on the mildew. But the "mildew" that makes black spots is Downey Mildew. It takes a microscope to be sure that it's DM and not Black Spot. And other symptoms appear for DM.

And Downey Mildew is a different disease that makes black spots... What I tried to write was that not all black spots are the same disease. "reports on Black Spot, Cercospora, Anthracnose and Downey Mildew"

When you remove leaves, you'll reduce disease pressure on that rose. But Patriciae said something very important: she wrote that the leaves are food factories. Lost leaves are losses to the rose.

And fungi are very simple: they reproduce by spores that are about 5 microns in longest dimension. They cannot be picked off, when you move an infected leaf, the shaken-off spores are spread by your action.

I normally think of Black Spot as the disease caused by the fungus called Diplocarpon rosae. (Click the link to see the picture.)

Once the entire leaf turns a black-spotted yellow, it falls off.

Where I grow, powdery middle only happens for a short time in the early spring when the nights are still cool. It covers a few leaves in a white/silvery powdery looking substance, but I've never seen it take over a plant entirely.

Henry, I read the article, and I think the Serenade product that Jeri recommended (thanks, Jeri) is something along those lines, though I think Serenade is a different species than those researched.

But even though I asked about an earth friendly product, while I was reading that article, I was reminded of the story of penicillin. Then I remembered those news reports about how years of overuse and misuse of penicillin had led to the development of super strains of bacteria that were not affected by penicillin and that new antibiotics were needed.

Do you think that even though things like Serenade are "good" that in the long run they, too, will contribute to an imbalance and super strains of Black Spot developing? And the ultimate solution really IS no-spray, choosing the most resistant varieties, and learning to accept a lack of perfection in rose gardening. As many people have been advocating here for years?

Here is a link that might be useful: Black Spot picture

I second the opinion, Bellegallica.
Live and let live.

Yes, Bellegallica, that picture link was what I was thinking of for black spot. Ann, thanks for clearing up my confusion on the mildew. I'm still debating what to do. I'm close to the "five year" mark, and wondering if I should see if it's just as magical for me as for others? Then again, I hear that BS lives in the soil to return the next year and I don't want to leave the cycle to repeat itself endlessly.

kinglemuelswife, if you are intent on not having it in your soil, then I feel that you will also not have any good bugs in your soil either and you will be locked into an endless cycle of spraying and high fertilizer growing.

http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.py.22.090184.001555

Here is a link that might be useful: Effect of sprayng

To control blackspot, especially in a hot humid climate, you need a shovel. It is used to dig up-- and discard-- roses which prove susceptible. Even in color classes most susceptible-- yellow/apricot/orange and lavender/mauve/purple there are a few roses which are resistant. The shovel is for the ones that aren't!

Agree with Olga, Double Delight should not be attempted to be grown no spray. The first two years I had roses, including Double Delight (and Peace), they had terrible blackspot, defoliated and did not bloom. When I started using fungicide, they took off and are now bloom machines. So if you want DD, you spray. If you don't want to spray, don't have DD.

There are other factors in play. I had other roses that were very blackspot resistant, they never had a spot. Then one year, they all had it, every single one. I think it was the very mild winter we had a few years ago.

I am using manure and alfalfa tea as fertilizer. I am eliminating roses that blackspot intolerably and replacing with more resistant varieties. Last year with these strategies, I noticed decreased defoliation from BS. It has never killed a rose or prevented from blooming in my garden. I just prefer rose bushes with leaves! Buff

Hi kingmuelswife,
This may not apply as much to your area as it does here - but making sure that the plants have enough sun and adequate surrounding air flow is probably important in BS control.

'Teasing Georgia' is supposed to be a bad black-spotter, but is clean in my no-spray garden. It may be because it is trellised and getting blasted by several hours of sub-tropical sun every day. I think the UV must be burning the fungus off. 'Double Delight' is also doing very well, gets many hours of sun and is not planted too closely to anything else.

Other than that, I don't know much about controlling BS without commercial sprays. I have read that 1 tblsp baking soda /1 qt water to make a spray works, but I haven't tried it yet.

In a climate as cold as yours, it would make sense that bad BS, as well as any other kind of infection/infestation, might affect a rose's ability to winter over. I don't really know, I've never grown roses in Z5.
Happy gardening,
Avalon

I am not sure blackspot has ever killed a rose in my garden, but I have put numbers of them out of their misery who were plagued terminally with it. Would they have died? Who knows but after you see years of blackspot, no foliage, a plant decreasing in size annually, you know Hospice is a good thing.

I assisted in replanting a public garden. Among others, they had ordered a dozen each of then-new J&P floribundas, OLOGuadalupe and (I think) Outrageous! They were well planted, well watered, well-nourished, but not sprayed. They defoliated repeatedly from blackspot. Many died the first winter (zone 7) and all were dead within 2-3 years.

Michael,
I kept forgetting to ask about them, they had looked so good, but then one year they were gone.
Ann

Ann,

Yes, and the grafts were buried, too. So blackspot can indirectly kill some roses in some climates.

michaelg, could they have been virused also?

Henry,

You never know, but they were brand-new J&P varieties, so I would guess not. No visible symptoms. They just should have stayed home in California, where I'm sure they do well.

Let me start by saying I am a relative newbie to hybrid tea roses, and I don't claim to be an expert in any way. But I live in a very rural area with a lot of "old timers" who live by the Farmer's Almanac are happy to share their tips and tricks. And more often than not, they seem to work.

I'm in the Ohio River Valley, and black spot can be a real problem here. It made my HTs almost unbearable to look at. They kept growing and even flowering, but lost many if not most of their leaves...and it spread from one bush to another almost like a plague. I was ready to give up.

But a very old man at our local feed store gave me these instructions, and it helped immensly. He told me to throw corn meal around all the bushes as far as the leaves can drop, and then spray them heavily with a milk and baking soda mixture....about half water, half milk and 1/3 of a box of soda in a gallon jug.

I did the cornmeal, sprayed every other day or so with the milk/baking soda...especially after rain, and picked off and discarded any fallen or infected leaves.

Might sound crazy, but it made a big difference. It didn't totally eliminate the problem, but it definately made a very noticable improvement fairly quickly. Can't say that it would have made a lasting improvement though because a hellacious ice storm pretty much devastaed the whole garden this past winter.

Either way, it's cheap, it's easy and organic, and it seemed to work really well during the growing season. So just take it for what it's worth and good luck with it all. I plan to do the same thing this year when I replant what Old Man Winter destroyed. :)

In a thread a number of years ago, it was suggested that the role of the cornmeal could be that it promotes the growth of the good fungus Trichoderma viride.

I Googled and found an earlier cornmeal thread that was still available:

http://forums.gardenweb.com/forums/load/lab/msg0420300313017.html

Here is a link that might be useful: early thread

The milk may also promote beneficial fungi.