Looks to me like mildew (the downy version).. Did you have prolonged coolish (15C - 23C) and very humid weather lately?

IF IT IS, I would use a chemical on it if it were my beloved and it should be one with curative effectiveness against rose downy mildew (Peronospora sparsa fungus). Strobilurins, widely used on downy mildew on other plants and most probably the class of drastic ingredients that will be advised to you by someone not expert on ROSE D.M., are NOT particularly effective and may only be good as preventives. I've lost track of the tens of chemicals banned or restricted in the EU lately and I do not know what may be available to you over there so I can't (and shouldn't really) recommend but systemic fosetyl-al (e.g. Aliette) used both as a spray and a drench a couple of times in a weekly interval may be a good bet both in terms of effectiveness and availability. Drastic ingredients mefenoxam, dimethomorph, mandipropamid and cyazofamid are also effective but it may be better to check locally for availability and legality of use. Applications should cover adjacent roses, if any, also. None of these chemicals used regularly will promote your health. Local EXPERT advice is always the way to go in such cases.

IF IT IS and you won't consider spraying then removing the rose should be on your agenta although I'm sure there might be other things to try, which I can't recommend since I have no clue about their efficacy.

Also look for signs on other adjacent roses.

Some of it LOOKS like downy mildew -- tho I would love to see more leaf photos, close up.

Some of it is blackspot. I'd worry more about the downy than the blackspot.

Aliette melted a plastic spoon -- after which, I refused to use it.

Avocado farmers here had better luck with a related organism (Avocado Root Rot) mulching heavily out to the drip line with FRESH horse manure -- so that's what we did -- and it did a better job than the chemicals did. YMMV ... but it worked for us then, and I would do it again.

No -- it does not kill the organism. Nothing really does. But it bolsters the plant's immune system, and aids it in overcoming the plague.

fosetyl-al will not melt a 'plastic' spoon. Some solvents used in pesticide preparations may affect some synthetic materials when in concentrated liquid form that's why measuring devices, tanks, sprayers etc should be of a material appropriate for use for agricultural chemicals. Over here Aliette comes in dry powder form which will not attack anything I know.

It is difficult to be sure if it is DM or not just by looking at pics as symptoms tend to be variable. A local rose expert or nurseryman will be able to recognize it, if DM is prevalent locally. DM is easily recognised under the microscope. There should be characteristic 'mildewy' fuzzy growth on the underside of the leaves but often it's hard to see with the naked eye.

Come to think of it, by looking at the state of those canes, I would use a couple of chemicals on it (may be one systemic for downy and a wider scope stobilurin based one or mancozeb) just in case. IF it were my beloved rose..

DM killed two of my rose which were giants, and 80+ years old. Killed them over just about 1-2 weeks. I would jump on this, and in this instance I would use chemicals which are specifically for downey mildew.

Jackie

Ugh. That was not what I wanted to hear - GT nearby is spotty too, but he often is, so I did not inspect closely, which I will remedy when I go out. I will try and get more pictures too.

The weather has been right for it I guess - pretty much all May has been mildly warm and damp, about 14-18 deg c and consistently overcast so it stayed warm at night - I put my runners and tomatoes out early because of this.

I can certainly do the fresh horse manure (keeping the dog off've it'll be the issue!) and that's something I can do immediately.

I can also treat with mancozeb to at least knock back the blackspot - I am guessing that maybe downey is making it more vulnerable to other infections? As this rose is not usually troubled.

None of the other chemicals are easily obtainable - or cheap - or readily available to the public rather than trade - however I can order Aliette from a german seller. *sigh* It's not cheap, however it's cheaper than replacing the roses in that area of the garden!

Is this a case where I should preemptively spray all the roses in the general area or only those clearly affected?

I can send you cheap Aliette if you wish. I can also exchange Aliette with a rose from a nursery in the UK.. PM me if you're interested. Problem is, if it IS DM you should act fast.

fduk, have a look at this discussion Kim started over at the Roses forum:

[https://www.houzz.com/discussions/downy-mildew-idea-dsvw-vd~3893372[(https://www.houzz.com/discussions/downy-mildew-idea-dsvw-vd~3893372)

Virginia

Ok, more pictures. Francesca seems most affected, closely followed by GT and GC. Buff Beauty nearby has a few spots, no cane marks. KPV looks revotibg but I think it's her usual mutant blackspot /crud rather than what Francesca has.

More Francesca

GT

GC

BB

Apologies for the photo quality, it's hard to get a phone camera to focus on a narrow cane. :(

I will order express shipping on the Aliette Nik, if you think it needs to be urgent. I suspect there would be little difference in the postge duration from Greece / Germany anyway. But the offer is definitely appreciated and of course the reciprocal offer holds if ever you need it - although admittedly, the chance of there being something you need in less regulated Greece that I can get in the UK is probably small!

The hot water trick makes me nervous, though I might try it anyway, the issue being getting sufficient quantities of hot water to douse with for several minutes, hooking up to house water heater being impractical.

It's just occurred to me that while I'm waiting for the Aliette, I do have a potassium phosphite fertiliser/fungicide, Uncle Tom's Rose Tonic which is a ridiculously twee name but I have used it to some effect on apple leaf fungi.

0:23:21 ratio. Worth trying in the interim? There seems to be some evidence of efficacy.

You could have both BS and DM. The worst symptoms of DM are that the leaves and canes start to DIE from the top. Die to crispy & brown, suddenly. Then, the dying gradually works its way down to the base of the rose. I am not saying this happens in every instance - just in the worst ones. I would still jump on this.

Jackie

I agree with both Paul and Jackie. MOST of that, at least, looks to me like blackspot. (I really wish I could see crisp images . . . ) There may also be some downy . . .
I just don't know that I would plunge into high gear with chemicals, but YMMV.

Sorry, had no time to answer the last two days. I'd certainly prefer it to be just blackspot - I guess it's just a different strain than normally prevalent, or possibly Francesca just manifests it differently.

Thank you for looking - I'm going to treat as BS for now - , i.e. prune off the blotchy canes and leaves, mulch heavily, water thoroughly, and maybe try the potassium phosphate 'tonic', and then when it's ready she can have a good dose of alfalfa tea.