I can't answer all your questions. I'm the type of rose gardener who doesn't spray anything for Blackspot.
Through trail and error I only keep the most disease resistant roses that do well in our garden, the rest go bye bye. But, the roses we keep, my wife and I still love very much.
But, I know, you didn't want to hear that. ;-) lol

Anyhow, most roses will still come back to life even though they have lost all there leaves to Blackspot.

I wish you the best of luck with your problem!

I have a no spray garden, and when my roses lose leaves, I spray with fish emulsion, available at any garden center. They leaf back out in a week. Good luck

The answer is that they will weaken over time and you will eventually lose them. I have a few that are so BS prone that they suffer even though I spray and what happens is they lose what vigor they have and they especially suffer if the winter is hard. Most of the purples are this way so if you want to keep them you have to give them extra TLC...make sure they are watered and fed well and sprayed extra well and in your zone they probably need good winter protection.

When I get a rosebush that defoliates from blackspot or any other reason, I cut it back to promote new growth from the remaining canes. I don't do this too late in the season though. I just cut back four 6' tall bare hybrid rugosas to 18 inches to activate new growth. They are growing in a sheltered location and even though they get watered early in the day, they do not dry off and develop severe blackspot and mildew. By mid September they should be looking good but I expect to lose much of that new growth this winter. The same varieties, Hansa and Magnifica, planted elsewhere in my yard, do not have this problem.

I use organic products to feed the roses, they work well.

The roses drop their leaves in late summer, but I've not seen any detrimental effect from this. They can re-grow leaves later.

When leaves fall on the ground I rake them into the ground to tidy up the area.

Alot of my roses are also defoliated completely except for a few seedlings. I just cut Chicago Peace down to about 2 ft. and took all the leaves that were remaining off. We can grow roses til mid November here so I am not too worry about the new growth hardening off before cold weather sets in. If you feed your roses all summer and water well they should grow more leaves well.

Thank you all so much,
I'm afraid to promote growth right now because I understand I'm not suppose to feed my roses as of Aug. 1. I think I'll try the fish emulsion. Maybe, between that and the cooler drier weather we should get, they will be o.k. I have one out front that is suppose to be a focal point. If it doesn't shape up, I may spray it next year, or move it. Jim, I'm sure your roses are lovely. I just obsessed about certain roses for so long, I can't part with them.
Thank you,
Kitty

Kitty,

There are still things you can do this season: Keep your plants hydrated and avoid wetting the leaves. In late fall, completely clean up all leaves and throw them away.
In very early spring while the roses are still dormant, spray the canes and surrounding soil with lime sulfer. Then when the leaves are completely open and before the first bloom, start spraying the plants with fungicide. Try alternating between mancozeb and tebuconazole (bayer product). Some members on here are so anti spraying even if it means letting their bushes die....ridiculous. Fungicides are there to help gardeners maintain a beautiful and healthy rose garden. I hope to see you post next summer and advise how well you roses are doing.

It's important that you are gardening in zone 4. If your roses defoliate during the season, they have to use stored energy to refoliate. This leaves them less able to protect themselves from winter damage with antifreeze (sugar) and less able to grow out vigorously in the spring. Tender, BS-susceptible roses like hybrid teas will grow weaker every year, if they don't die in the first winter.

See the FAQ on the Organic Roses Forum for organic sprays, which include sulfur, anti-transpirant, and oil-bicarbonate mixtures. I used micronized sulfur with reasonable success for a decade and can recommend it. You have to apply it faithfully every week, because it is not as effective as the best synthetic fungicides.

I had black spot severely early in the season dure to a lot of rain.. I think the key is to daily pick off any old leaf that shows any sign of it at all as the new leaves form. Absolutely examine the underside of the leaf as it appears there first. One dot on the underside and I yank it off. Second, get those leaves away for your plants immediately and into the garbage. Thirdly spray. After a week or two it should subside and the plant sort of grows out of it. Chicago Peace is my favorite rose but seems to be the most susceptible to black spot.

Yes, I have tried organic methods successfully. I'll post info. and research links on that in the Organic Rose Forum next week.

Here's a picture of my Paul Neyron, most notorious for blackspot, taken after 3 subsequent bouts of all-night rain and humid weather in Chicagoland. It took me 3 times moving him, and 4 months of experiments before I figured out how to keep him clean without spraying. I used a potting soil with 55% fine composted pine bark (has tannin as a natural fungicide), lime (a natural fungicide), peat moss, vermicullite, perlite, and gypsum.

In agriculture, the highest yield of soybean was recorded using lime pellets and sulphate of potash, which beat the yield using fungicide alone. Horse manure is many times higher in potassium than cow manure or compost, and I used it succesffuly last year to keep my 10 Austins clean after 1 week of continuous rain in the fall. The stable here uses lime to deodorize their stall, which acts as a natural fungicide in the manure. Horse manure on wood chips does not absorb water like decayed mulch, thus stay dry and blackspots can't germinate. Potassium is needed to fight diseases, bloom production, and to counteract the salt index in fertilizers.

Here's a picture of Radio Times, another blackspot-magnet, taken today at 70% humidity. He's always clean in my garden, regardless of the weather. He's planted next to a cement patio with limestone base. My water is also high in lime (calcium oxide).

Strawberryhill -- fascinating post! I used a lot of banana peels on the roses I grow in containers, but not so much for those in the ground. Banana peels are supposed to be rich in potassium. My roses in containers do not get any blackspot, but those in the ground do even some of them are of the same variety. I always thought that it is because the potting soil I used is acidic (and thus inhibits fungus), but maybe those banana peels helped too.

Any kind of normal fertilizing program will supply ample potassium, and most soils retain potassium very well. Since most garden roses get more potassium than they can use, and still get blackspot, potassium fertilizer cannot possibly be a solution to the blackspot problem. Likewise, roses growing in alkaline soil have been getting blackspot for many centuries, and this has never been considered a way to avoid blackspot. Since blackspot will subside temporarily owing to weather conditions (including hot summer nights), spot observations by gardeners can be misleading.

As we've all been lamenting, this has been an abnormal year.

Daytime humidity in Illinois is nowhere near normal. It's been below 50% for a majority of the summer, and although humidity climbs during the evening hours to nearly 80 or 90%, it's fleeting, and the temps have not been in the range necessary for blackspot germination when the humidity peaks. It has been at or around 80 each morning before 8 AM.

Lots of folks have been complaining about the humidity here (locally, not on the forum) without checking weather stats. They're surprised to see that it has been low since they are used to wet, sticky summers. As I type this message, it's at 32%, down from a high of 80% overnight.

I haven't had the need to spray for over 2 months. Time and effort has been spent deadheading and watering--that's it. Good soil is dry to 4 feet down; our clay was dry to at least 18 inches. I stopped digging at that point. I've never seen water sink into clay & disappear like it does this year.

Everything I have is planted in clay & the roses do fine, and WILL get blackspot if conditions warrant it. This year, it was only a danger in late spring.

In the past I grew about 1000 roses in a northern Ohio zone 5 garden. I did not spray. I would get a little blackspot on some roses late in the season. I have stated that I consider that as possibly part of Nature's way of shutting down the roses for winter. 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:

[sorry link no longer works]

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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

MNKitty:
I have roses in the Hutchinson and St.Cloud area.

The heavy soil down by Hutch is more prone to black-spot than the sandy soil up north but I use Serenade on both and it controls, to eliminates, the black-spot well.

This summer up North I only had it where I put in a new rose but down by Hutch, where I did not get as often late in the summer, late in the summer it showed up but I treated the roses, and had no defoliation problems.

I usually pick off as many leaves as I can before I treat but this year my roses in both gardens did not get as much attention as they normally would so I picked the worst and soaked the rest.
The black-spot marking remains on the leafs not picked but they remain green and do not drop as the black-spot is usually dead, and remains like a scar.

Serenade is organic and has workded very well for me.
Buy the two and one-half gallon containers and you will save a lot of money.

It is not perfect though and you will have to try to attend your roses well.
Picking off and discarding affected leaves reduces the misery a lot compared to just treating.
Also beware of newly boughten roses, that is where I have most often ended up with black-spot where I did not have it before.

I have at time at time pulled the roses, cleaned and soaked the roots, sometime just soaked the entire root ball, in a Serenade bath while attending to the soil by digging out the soil as many inches beyond the drip like as possible (no more than three) and down approx. sixteen inches and putting in new soil.
I have done this down by Hutchinson also at times simply to replace the very heavy black gumbo down there as I have to walk through the garden and while it does not kill the roses, the soil is very rich, it makes burying them in the winter easier.
That it removes black-spot sitting in the soil is a bonus.

I have lost few roses to winter, and none to black-spot but spring shock, i.e. uncovering healthy roaes but losing them to a late spring cold snap, has been horrid in these warm winters we have had for the past decade.