Cercaspora, looks like from here, but my eyes are not what they used to be. Could it be Downy mildew?

I call it blackspot, but it is a bit different from blackspot on other roses. Before I fixed the nutrient problem I had for years on Rose de Resht, it too got something that looked a bit like this. But it was not only on the edge of the leafs.

Because it is a dark discoloration mostly on the edge of the leafs, I think it might be some type of nutrient deficiency. Only old leafs, or new growth too?

I've never gardened on the West Coast (or lived there, for that matter), but to me it looks more likely to be a nutritional disease (nutrient imbalance or deficiency) than an infectious disease.

My first thought was that it was burned, either with fertilizer or a hortucultural oil.

We need Michael? Ann?

Did you put anything on it?

Sammy

No, I did not put horticultural oil on these plants. The last time I fertilized was in May with a very light fish fertilizer. This stuff only shows on Penelope and no other roses. I have to look if it is on new growth or only on the old growth. I know the picture is not very good. In googling rose diseases today, it looks like Downy mildew which I never heard of. My concern is that it might spread to my other roses.

The symptoms are right for phosphorus deficiency, although I've never seen it on a rose.

Fish fertilizers alone are not that good for roses, as they mostly contain nitrogen and little else. If you only use that, it might be the explanation. Kelp / seaweed fertilizers are better, as it contains lost of potassium, all micro nutrients imaginable and some nitrogen, but no phosphorus (bone meal does, manure and compost) A rose fertilizer with all the NPK nutrients is a must in the long run. Most soils contain phosphorus enough to prevent deficiency symptoms, but very sandy soil are known to do so.

I am always pleased to see Malcolm post, and we know that what he says is true. If it were downy mildew, he probably would have mentioned it. However, around here we don't have downy mildew, and that is the one problem you have in California. If Jeri does not post, you might email her. She is very familiar with that disease.

Here, when it is very hot, if we make a mistake and add the wrong fertilizer, or spray at the wrong time, we can get those symptoms. We can also get them if the rose is not fully watered, and we spray.

Sammy

Fertilizer burn or salt stress typically shows burnt areas around the edges of leaflets. You could have salt accumulation in old potting soil if you don't water enough to flush the soil. CA irrigation water is salty and so is fish emulsion. Water evaporating from the soil leaves salts behind. Consider changing the soil and increasing the water. Avoid terracotta pots, which absorb salts.

I agree with others that you should be using a more complete fertilizer such as MG or Dr. Earth. It's possible there is some nutrient deficiency.

Chronic downy mildew is restricted to very cool coastal climates. It attacks the new growth first or primarily and usually kills leaves quickly. It needs rain to spread.

I am pretty new to roses, but I'm posting because one of mine had something like that. It's an old Hybrid Tea called Nigrette, and it's been in a pot for not quite a year and a half. I saw a picture of salt damage on the internet, and it seemed close to what my rose's leaves looked like, so I flushed the pot. However, that didn't really seem to help, so early this summer I repotted it into a larger pot (plastic, not terra-cotta, which is what it had been in), and it has since grown and thrived and no longer has those dark spots/areas at the edges of the leaves. I should mention, though, that my leaves included yellow at the edges before turning dark.

And thank you to Dr. Manners for that information about salts and terra cotta. I'm glad to know that and will change my ways.

Oh, I apologize to both Malcolm Manners and Michael G!! My brain seems not to be working on all cylinders today...

I'm honored to be confused with Malcolm :)

Just to clear things up, Penelope is not in a pot but in the ground. Besides fish fertilizer, I also feed my roses alfalfa pellets (in spring) and in late April some Miracle Rose Food - yes, I know some people will dispute that this is good for the soil. As someone suggested above, I will give it some seaweed and perhaps some Dr. Earth #8 that I feed my plumerias with. Thanks for all your input.

Obviously, you do not have downy mildew. Sorry for the intrusion. If it was downy mildew, the leaves would turn yellow following the purplish/blackish demarcations and fall off. I think what I was trying to think of was botrytis blight, but I don't see any holes. I am sure Dr. Manners and/or Michael know. Sorry to have confused the issue, but here is an article on Downy Mildew just for posterity.

Downy Mildew

Introduction
Downy mildew causes foliage blights and distortion. Although its name sounds similar to powdery mildew, downy mildew occurs during different environmental conditions and it is managed differently.

Downy mildew is not as common as foliar blights caused by Botrytis. During cool wet weather, downy mildew can occur very rapidly and is difficult to control. Some of the greenhouse crops prone to infection include: snapdragon, salvia, alyssum, pansy, rose, rosemary, and ornamental cabbage. Perennials susceptible to downy mildew include aster, coreopsis, geranium, geum, lamium, potentilla, veronica and viola.

Symptoms
Symptoms can be confused with other plant problems. Leaves may become mottled and yellowed, resembling nutritional deficiencies. On some plants, downy mildew infection may look similar to injury from foliar nematodes. In both cases, angular lesions are bounded by leaf veins. However, downy mildew infection results in a soft, fluffy gray, brown or purple fungal sporulation developing on the underside of leaves. On coreopsis, the fungal sporulation is white.

Symptoms can also vary depending upon the host plant. On snapdragons, infected plants are yellow and stunted. You may see downward leaf curling on the young seedlings. On salvia, angular yellow blotches can be seen between the leaf veins. On pansy, leaves turn mottled and off-color with purple blotches. Pale green or yellow patches develop on geum. Purplish patches occur on lamium and veronica.

On roses, leaves develop angular dark purple to black areas and may turn yellow and drop.

Another point, downy mildew on roses does not usually produce noticeable fuzz on the underside of leaves.

I have this also here in San Diego. Pillow Fight had it then didn't, then now does again. So a couple months without. Oh yeah also, Fragrant Cloud. It did seem to crop up after major heat wave. (I know there are more... to sleepy to go look right now)

Do not know what it is. All roses are new to me or newly planted in ground that have it. They are in different beds too. Yeesh, hard to nail down.

Allison

Allison,

Salt/heat/moisture stress in all likelihood. The three are interrelated. New plants are more susceptible because they have smaller, shallower root systems. Give them supplemental water.

Looks like salt burn. "Salt" covers a lot of ground, from the salts in fertilizers and amendments to simply high sodium soils or even salt spray from windy storms near the ocean. It could be excess calcium, potassium or phosporus, or sodium. I'd try to flush the salts out of the soil with a good deep watering, washing the leaves down too.

Here is a link that might be useful: calcium burn

If it was a rhodie, I'd say it was salt burn, but it's a rose, so I'll say nothing

Since they are in pots, would it be wise just to change the soil in the pots and wash the plants/roots really well. I think flushing the ground/soil might not be beneficial in the case of this being potted roses.

Michaelg,
Thank you for the info. I bought the Pillow Fight tree (7' tall) and it had obviously been in the pot way too long. The salts could have built up in the container and I haven't flushed them away yet? (It is in ground now but with old soil intact.)
I have had a bad habit of over watering roses in the past. It's frustrating to see the yellow leaves all over two days later.... Maybe I have been too cautious?
Worth a try!
Thanks.

Allison