In a warmer climate where winter stress is not a factor, defoliation from black spot would not be as serious a threat as it is for your roses to successfully go through your up coming severe winter conditions in your Toronto area.

Roses store energy in their canes. The stored energy comes from their leaves, which are the bush's mouth, stomach, and bowels (the food factory), of a rose. The roots supply water and nutrients to the leaves. Part of a rose's 'waste' it produces, is the oxygen we breath.

If a rose loses its leaves, it draws upon its stored energy in it's canes to produce more leaves if growing conditions are favorable. If it loses its leaves normally in the fall, the stored energy in the canes feeds the new leaves in the spring.

If you have a warm fall, your roses will continue growing, and pushing out new growth. The drain on the roses since there are so few old leaves to feed and sustain this fresh growth will weaken your roses even further. Fertilize them now to compensate the drain on them, and the new growth made is even more susceptible to winter kill, being tender, late season growth.

You're essentially in a "Catch 22," situation. Almost nothing you do will rectify the loss of the black spotted roses' leaves, this late in the season.

I therefore suggest you do nothing now. If you usually winterize certain of your roses continue on schedule this fall.

Come spring, you will see what to do. You will probably have a fairly good bush survival rate, but expect some significantly drastic pruning back of winter killed growth, even the winter protected roses will likely have more dieback than usual.

Don't let your roses lose their leaves this late in the season. Losing their leaves earlier in the season, if the loss is halted, gives the roses time to recover their strength.

Moses

The first thought I had was the clean up part. It's a joke honestly. If a rose is prone to back spot no matter how well you clean up. It will still black spot.

I agree with Mosses in that we live where the season is short and winter weather is harsh. Rose need to be healthy and stay heathy to gather as much strength as it can to survive. It's no different than us if we are heathy and get the flu things are usually okay. However if we are sick or have a disease the flu is far more likely to kill us.

My suggestion would be to pick up a fungicide if the leaves start to regrow. They need all the help they can get. In spring they may come back nicely but they will not keep that up every year. So I basically said what Mosses did just a little differently. If your roses get black spot they need a fungicide in order to be a good performing rose.

However, Dr. Buck planted his roses out where the corn grows in northern Iowa to test them. Most of those roses do black spot. I saw a chart once will like 15 of his roses and the percentage of leaf loss at various times of the year. Those babies were given the toughest growing conditions a rose could dream of. They came back every year.

Nothing like a good contradiction is there. I can guaranty you that Griffith Buck knew more about roses than I do. He most likely dumped many roses that could not recover well thou.

Clean up diseased leaves that are laying on the ground if you wish but I never do... When you cut them way back in the Spring cover your soil under & around roses with new compost or mulch...

I (and I have seen others post something similar) wonder if fall blackspot is not part of Nature's plan of putting the roses to sleep for the winter.

Dr. Buck sprayed. He wasn't really interested in tough roses.

First question, are you absolutely positive it is blackspot? It sounds more like some other spot disease.

"While he was a professor at Iowa State University, Grifth Buck developed more than 80 new rose cultivars, primarily shrub types, which were released between 1962 and 1997. A primary aim of his breeding program was to develop cultivars that were sufciently robust not only to survive Iowa winters (with minimum temperatures as low as –35 C), but also to retain their foliage all season without fungicide sprays."

http://horttech.ashspublications.org/content/18/4/588.full.pdf

Lily (and the roses) say otherwise. It is rather surprising that the roses get finickier as time goes by. For most breeders it seems to be the opposite. But compare Applejack and Distant Drums, and the difference is obvious.

I'd make sure they were kept adequately fertilized and clean up the fallen leaves to reduce future infection potential.

I wouldn't expect fertilizer applications made now to result in spring-like bursts of tender new growth that got frosted.

I seem to always get a good case of black spot in the fall too. It has a lot to do with the weather conditions being just right for the spores to grow. You can clean all you want but you'll never get rid of all the spores. They're everywhere. I don't spray so never do anything about it. I've never noticed that it made any difference in a rose's winter survival.

When black spot hits my roses it's always from the bottom of the bush and works its way up the bush. The oldest leaves are the ones lowest down on the bush. It stands to reason that the older leaves are more hospitable for black spot to develop. Besides their closer proximity to the soil where black spot spores are heavily concentrated, I believe it is their age and lowered immunity due to their age that enables black spot to hit them first.

Once black starts down below, and leaves begin to drop, the bush starts stressing. In its stressed state the black spot works its way up more easily, and colonizes younger and previously more resistant leaves, that are now weakening.

Come September, there are leaves on my bushes that are 6 months old. If black spot starts to show on them I consider it acceptable. They are worn out, and soon will drop naturally, black spot or not. Any black spot stress is negligible. Rarely do these spotted leaves even drop off until after a few frosts, pretty much as if they had no damage.

Now, black spot earlier in the season is a different story. It gets the full arsenal. Rarely do I let black spot get a hold since I use fungicide pretty religiously.

Moses

Ironically, my BS magnet is Brilliant Pink Iceberg. It is ironic because my garden is filled with fussy HTs and this rose is a sport of Iceberg, which I understand to be a highly profitable landscape rose in California. It gets BS and loses a lot of leaves every year. Which means I have clean HTs and a blackspotted landscape rose. What this really means is that you shouldn't grow Iceberg or its sports in New England.