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Does anyone know what this rash is on my roses?

2 years ago

Hello All!!! I hope everyone is having a lovely day. I was wondering if anyone could tell me what this disease is on my roses. I have attached a picture of the leaves. This plant has already bloomed beautifully, and then this. Perhaps it is nothing, but I'd rather take no chance. If anyone could diagnose, let me know what action to take ... it would be greatly appreciated. Thanks!!!

Featured Answer

Moses, Pittsburgh, W. PA., zone 5/6, USA

2 years ago

last modified: 2 years ago

The best cure for black spot is GROW BLACK SPOT RESISTANT ROSES! Black spot resistant roses are coming out from the rose breeders more and more each year, from: bushs like the Knock Out series, ground covers like the Drift series, floribundas like Poseidon, to even hybrid teas like Pinkerbelle. That's your best bet to grow roses having the most pristine foliage without having to spray them.

May I respectfully ask you to examine the underside of your leaves for spider mites.

I do not see strong evidence of a black spot infestation in your sample leaf. Black spot, it may be, but usually several black, roundish, fuzzy-edged spots of varying sizes are present on a rose's leaf, often turning the leaf a bright yellow before it drops off. There are several strains of black spot, though, each with its own visual appearance. The most common black spot strain's symptom is as I just described. An individual spot being up to about 3/8" diameter, and adjacent spots do grow into each other making for a much larger 'community,' spot to 3/4" across, but usually not circular in its shape, but irregular.

If it is a fungus, looks more like Cercospora leaf spot because the spots are not black, but tan/gray in color, particularly at their centers. However, the difference between the two, cercospora leaf spot and black spot, is a difference without much distinction. Both are harmful rose fungi. Athough in my garden, black spot is more deadly. BS can kill a bush at the worst, and at the least, weaken it until it performs very poorly. Cercospora is a little less deadly.

Moses

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Comments (8)

JoJo (Nevada 9A)
2 years ago
Where are you located? Your location would help with the diagnosis.

It could be blackspot (fungus), or the beginning of something else. Do you see anything forming on the underside of the leaves that look like orange blisters?
Mary Byrne
Original Author
2 years ago
I am in Wilington, NC ... no orange blisters as of yet.

Here' s a picture of the underside.

( a bit wilted now)
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Where do you have that pot? The picture appears that it might be indoors. Is it? If it is, put it outside immediately. That is a pretty ornamental pot. However, it looks way too small for a rose to grow in. If you get a LARGE clay pot (not glazed), and re-pot it again with good potting soil, and put it outside, it will be much happier. Put the pot up on some sort of pot feet or other thing to keep it up 1-2 inches (any nursery has things for that, as well as unglazed clay pots) so it will drain. VERY IMPORTANT. If it has been indoors, put it in partial shade for about 3 days, and then move it into full sun. I would cut off all of the blooms and buds, and just wash the black stuff off the leaves gently. I have no idea what that is, but what will help most is getting the rose into a large enough pot outside which drains well. It looks like some sort of fungus. After you get the rose into a large pot outside, and then move it into the sun, see if it comes back - it probably won't. If it does and you want to spray it, get Bayer Advanced Disease Control at your nursery, and follow the directions. NOT any of the many other Bayer products, such as "Three-in-One", "Two-in=One" - they contain poisons you don't need which kill bees and good bugs. Pretty rose - good luck! Jackie
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Jena, my Perle d’Or did the bud drop thing it’s first year, the whole year. A lot of my roses also had chlorosis, including Perle d’Or, even though they were getting regular Magnesium-sulfate and I was alternating between Miracle Grown and a seaweed fertilizer, all in the hopes of curing them of chlorosis. Mostly it was the Polyanthas and Multifloras that had this problem. Finally I sent in a sample for a soil test. I had plenty of all the minerals and nutrients except for Nitrogen (which I already knew since its obviously devoid of any organics and so I was fertilizing) and absolutely zero Manganese (Mn) detected. Once I put a teaspoon of Manganese Sulfate dissolved in a gallon of water on each rose last fall the chlorosis completely disappeared and Perle d’Or stopped dropping buds. I will now do this once or twice a year; not too often since Mn is a minor nutrient and too much can be toxic. The Miracle grow I was using did have trace Mn, but somehow it wasn’t enough. I wonder if my soil was just binding it up? This just demonstrates that bud drop could be due to lack of an essential nutrient. It might not necessarily be Manganese for you. But since you mention the Kellogg soil might not be that great, I would give it a nice dilute liquid fertilizer once a week and see if it cures it.
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Mary Byrne
Original Author
2 years ago
I suspected black spot as well.
JoJo (Nevada 9A)
2 years ago
last modified: 2 years ago
I agree, based on your location and the pic, I think it's blackspot. There's a ton of information out there and not all of it accurate (i.e. a lot of home remedies that are useless or may even harm your rose).

Speaking from experience, you can 1) live with it and accept that your roses won't look good for a portion of the growing season; 2) replace it with a blackspot-resistant variety, or 3) start spraying chemicals. The latter option is not a one-time fix -- you would have to start a regular fungicide program.
Mary Byrne
Original Author
2 years ago
Thank you so much for your reply. I just pruned it very hard, and started spraying. You think I'll have any luck? Or, once it is afflicted, it will always have black spot?
Mary Byrne
Original Author
2 years ago
... in killing it that is.
JoJo (Nevada 9A)
2 years ago
The spores will always be there, that's why annual, regular spraying is necessary IF you want clean roses. I used to garden in Maryland organically, so my roses were a blackspotted mess. Some would lose all their leaves by mid July. Only Knockouts stayed healthy all year round.

I have since switched to resistant varieties, even though I don't get any plant diseases here in the desert :) I hope your case is less severe and more manageable than mine...

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