Kop-R-Spray and sulfur are the two products listed against black spot in Oregon.

That said, you need to understand that fungicides are preventive. In other words, they protect new growth against infection. They don't get rid of, or decrease, existing disease.

Further, this winter & spring has been particularly favorable for leaf disease. Black spot is just one of the many.

Information from Oregon State University says this:
"Focus applications at the beginning of the season starting at budbreak. Apply frequently in wet spring weather and occasionally in summer (1- to 2-week intervals). May be very difficult to manage once the disease gets started."

That said, cultural management is also required:
Cultural control:

1. Plant cultivars known to be resistant
   (It's obviously too late for this in your case. But you could consider replacing the rose with a more tolerant kind.)
2. Avoid dense plantings and shaded areas.
3. Avoid overhead watering that keeps plants wet for extended period of time. (Hmmm. This goes for rain, too. Unfortunately,no way to stop that!)
4. Rake up and destroy all leaves in a rose planting at season's end.
5. Prune canes back to two buds if canes are infected. Remove and destroy diseased canes before budbreak.

I'd recommend neem oil. Approved organic and one of the best fungicides on the market for roses.....look for it under the label 'Rose Defense' by Greenlight but also sold by various other suppliers. Neem oil is also highly recommended by professional rosarians and the American Rose Society.

One of the other benefits of neem is that it is also an effective pesticide for soft bodied sucking insects - like aphids - so you get a double hit with this product, both insect AND disease control. As jean indicates, as with other fungicides, it is only a preventative, so you need to apply before you see signs of the disease to achieve complete control. And you will need to reapply periodically.

FWIW, roses in the PNW are just going to be very prone to fungal issues, "disease resistant" or not. I have yet to see a variety of rose, even very tough rugosas, that did not experience some sort of fungal issue at some point in time. But some do experience less of a problem.

Nine cultivars were resistant to all three races (Brite EyesTM, âÂÂGrouseâÂÂ, Home Runî, Knock Outî, PaprikaTM, Peachy CreamTM, Pink Knock Outî, Rainbow Knock Outî, and Yellow SubmarineTM)

Here is a link that might be useful: Evaluation of Roses from the Earth-Kind® Trials: Black Spot (Diplocarpon rosae Wolf) Resistance and Ploidy

I had not had great success using Neem for blackspot, it does have some good results against insects. I tend to eliminate the roses which are prone to disease myself, I don't use sprays or chemicals any longer.

I would recommend if you do use Neem Oil, make sure the temperature isn't going to go above 80 or it will fry the leaves! On the other hand, given our recent cool spring temps, maybe this won't be a problem this year LOL... ;-)

My Knock Out roses have had blackspot in the past.

{{gwi:1077652}}

That doesn't look like black spot to me, maybe it's bacterial leaf spot.

Personally I agree with GG and the Neem, start weeks ago, and that particular spot is always going to be problematic for fungus. Roses and turf are a great combination for disease problems.

Dan

I've grown multiple different kinds of garden roses for years that do not get black spot.

Buyorsell, that's anthracnose, not blackspot. Hard to find fungicides labeled for anthracnose on roses and it doesn't generally respond to the fungicides people use for blackspot.

Neem oil is horrible. I do not recommend it to anyone. Not only is it worthless as a fungicide unless you have very little fungus disease pressure to start with, but it also kills ALL soft bodied insects including many beneficials, such as larval ladybugs, larval lacewings, and minute pirate bugs.

I have tried it a few times, different brands, in different gardens. Same results every time - no effect on blackspot, and outbreaks of mites and aphids from the loss of beneficial predators. In our area there's rarely any need for insecticides on roses so no reason to use a combination of fungicide and insecticide anyway, even if it worked on the blackspot.

I second the sanitation and early intervention recommended above. Kinda late now, judging from the OP's photo. Strip off the bad leaves, prune off canes with lots of purple spots (that's blackspot too), and start spraying regularly with something, anything, labeled for blackspot that you feel comfortable with. Sulfur and copper are very old remedies for fungal diseases. I use the heavy artillery myself, albeit at the longest spray interval recommended, and my dogs all seem to lead long healthy lives, for what that's worth.

good to know, thanks

Hi ellen_Portland

I had such an issue with black spot that I all but stopped growing roses until I found that some roses are natuarally disease resisitant to BS.
Here's a list that grow and found to be really tolerant of BS.
Gourmet Popcorn - Miniature shrub - BEAUTIFUL and tough as nails.
New Zealand - HT
Gemini - HT
Honor - HT
Easy Going - Floribunda
Baby Blanket - Landscape Shrub
Livin' Easy - Floribunda
French Lace - Floribunda
Penelope - Large Floribunda
Sally Holmes - Climbing
Playboy - Shrub
Hot Cocoa - NEW - So I'm not 100% sure of how resistant it is.

As for spraying, I use Neem oil but I find that due to their natural resistance that I don't have to be very strict with the spray schedule.

Jean001a: A fungicide kills fungi; sulfur and copper based dormant sprays are preventative, but do not kill fungi that are present.