I've battled blackspot for decades in Texas, New Jersey, and Arizona. IMO things were worst in NJ. I found very few HT roses did well. Midas Touch, Electron, Big Purple, and Olympiad, I think, were the only HT roses in my garden at the end of a decade of rose gardening; the rest (probably upwards of two dozen cultivars) died of black spot. Some, like Don Juan, bloomed once or twice before dying. Most did not. Gardening in AZ has proven little better, though I might add Folklore. Hybrid musks Felicia and Buff Beauty did well. Seafoam, New Dawn, and Playboy did well. So too, the climber Zephyrine Drouhin. I was happy with the David Austin roses Sophy's Rose, Mary Rose, Mary Webb, and Tess of the d'Ubervilles. I had some middling success with Scarlet Knight and Tournament of Roses (both grandifloras). I believe the multiflora element in them gave some protection, but I believe they succumed. The Griffith Buck rose Carefree Beauty was wonderful. (By contrast, Carefree Wonder made me wonder why it was named that.)
Griffith Buck roses generally have done well for me. I grow April Moon and Prairie Star here in AZ. Quietness, a glorious rose, collapsed from drought one year, although I suspect some gopher activity might have been involved. In any case, these roses have been pretty clean; and I would try any any Buck rose without hesitation. Similarly, many of the roses in the Canadian Explorer series are quite resistant.
I found Radler's Knock Out to be completely free of black spot. It was nicely branched and it tolerated some shade. I was surprised to find the blossoms lightly fragrant. I found the raspberry red bloom to be remarkably garden friendly. It's not a good cutting rose, perhaps; but it can be a wonderful garden plant. If I gardened in a place like PA or OH, and could grow just one rose, this would definitely be on my short list.
Here in AZ I garden in an arroyo. During the monsoons in July and August the air can get really damp and blackspot is an issue. I have been reminded how some of the early David Austin roses were blackspot magnets in NJ, and have had to sequester Winchester Cathedral because two years in a row it seems to have started the plague and infected the surrounding six or ten roses. Cressida, when I grew it in NJ, was probably worse. These two roses are, however, far more vigorous than most HTs and grandifloras, so they recover. Golden Celebration is right on the cusp. It is almost as prone to blackspot and not quite so vigorous. I was only just able to keep it alive in NJ. Here in AZ it's still a problem but BS does not create an existential crisis for the plant every single year as it did in NJ. I suspect Princess Alexandra of Kent might be as bad.
Crocus Rose and Lady of Shallott seem to me to be at the other end of the spectrum, hardly ever showing a spot of disease. I'm pleased with Claire Rose and Abe Darby in terms of disease resistance. Graham Thomas has been pretty clean. So, too, Ascot a HT with a cupped blossom resembling a DA rose and bred in Germany.
As a general rule, roses bred by Kordes or other German breeders (see Pallatine Roses as a source) tend to be less blackspot prone than roses bred by California breeders. Kardinal is a notable exception. I did lose it to blackspot. Bright yellows, reds, and oranges tend to be the most prone to black spot, but Berolina, Europeana, and South Africa have proven to be almost completely disease free in my experience.
Grande Dame, bred by Carruth and introduced by Weeks, seems completely free of black spot here in AZ. It's the only Carruth introduction that has not failed by one measure or another in my garden. (Apropos of nothing, it's also among the most resistant to our strange freeze-thaw cycling of all hybrid teas I've tried here. It does, however, grow into a great hard-to-control jumble and has not been very generous in bloom. For this it is on my shovel-prune watch list.)
Some minis do well. I don't think I've ever seen blackspot on Red Cascade, Gourmet Popcorn, Magic Dragon, or Rise 'n' Shine. Cupcake might not be quite so clean.
Some of the classic polyanthas are quite clean: Marie Pavie, Phyllis Bide, Caldwell Pink, Katherina Ziemet for example. Ditto some of the classic gallicas: Desiree Parmentier and Felicite Parmentier. The china rose Hermosa lacks fragrance but it has never shown any proclivity to black spot. Many rugosas have good blackspot resistance. A number of the wichuriana hybrid climbers such as New Dawn, City of York, and Rene Andre seem just about as immune. Wichurianas, though, can be a little more prone to powdery mildew.
As mentioned above, most hybrid musk roses seem to be pretty clean, although Ballerina always seems to suffer from black spot until the rose is well established. The climbers Zephyrine Drouhin, Ilse Krohn Superior, Red Eden, Chevy Chase, Malvern Hills, and Mme Alfred Carriere seem to be almost completely unaffected by black spot. There can be light spotting on old leaves that have come through the winter having not dropped from the plant.
Floribundas are a mixed bag. I've been completely wowed by Cherry Parfait, Day Breaker and Rainbow Sorbet. I've been disappointed by Sunsprite. Sunflare did well for me in NJ. I've never been able to get Iceberg to grow, so I don't know whether it's any good. Europeana certainly is. Pink Parfait has its moments. I have a whole bed of the vaunted Julia Child, and it succumbed to BS last year. Very disappointing. Harsh measures will be taken this year. I began spraying in February.
Marchioness of Londonderry seems immune. That's a great rose in an understated sort of way. It's an ARE offering bred in Northern Ireland more than a century ago. In general, the roses found at Antique Rose Emporium are pretty resistant to blackspot because much of the early stock was collected from Texas graveyards where roses grew untended for decades. The Earth Kind line of roses found there are reputed to be exceptionally disease resistant, even by ARE standards. The only rose that will survive the whole long list of insults (deer, javelina, blackspot, drought, poor soil, and so on) afforded by my unfenced front garden is Pink Pet, sold at ARE as Caldwell Pink.
In gardening, it seems to me, nothing is ever completely certain. Only a miniscule portion roses in commerce are completely resistant to all insults. Some roses prove completely free of rust or powdery mildew on the West Coast where these afflictions are common. These same roses may be found to be instantly defoliated by blackspot when planted more than 200 miles east of the Pacific Ocean. Similarly, roses found to be resistant to blackspot throughout the eastern 3/4 of the nation might be gobbled up by powdery mildew the moment they are planted in a zip code beginning with an 8 or 9.
I hope these guidelines and examples prove some help.
