Thank you for both references Paul. The pictures are very helpful. I think my issue mainly is anthracnose right now. I’ll be checking for purple canes now as well.
If you are selecting for blackspot resistance, you may be selecting incidentally for susceptibility to Cercospora. They seem to correlate fairly well in my experience. I wonder if wichurana blood may be the connecting factor. Some varieties that come to mind are Mother of Pearl, The Fairy, Les Sjulin, Prairie Harvest, Belinda’s Dream (I think it is Cerc. on BD), various Meidilands, various glossy-leaved climbers.
Cercospora is a significant problem here in southern Appalachia. Spots appear in the early season. Unlike BS spots, they show through to the underside. After some weeks or even months, they spread into large dead patches (half a leaflet) and eventually the leaf dies. Spores are released from the stomata, and fallen leaves are a source of reinfection. Tebuconazole fungicide does not control it well. I don’t think it spreads much in really hot weather.
I don’t see anthracnose much. It seems to prefer cooler weather. Therese Bugnet and John Davis are two that were susceptible. The center often falls out of anthracnose spots, leaving a hole. There may be purple smears along with the spots.
Michael,
All I know is that I’ve tried to use parents that were very disease resistant and selected seedlings that didn’t show signs of leaf spots. As mentioned previously I have some seedlings that show no signs of any kind of leaf spots. I can’t comment as to any correlation concerning selecting for BS resistance selecting incidentally for cercospora susceptibility. It would be interesting to get comments from those who may have more knowledge on that than I have.
I do know that I’m having a bit of a tough time identifying between anthracnose and cercospora on plants that are showing signs of leaf spot.
To have funghal deseases is no guarantee that you have all strains. You can believe to some rose resistance for years until it meets the virulent for it strain.
At my field’s semi tropical environment, french Riviera, spot deseases resistance breakdown is common place i.e. Pretty Lady was immune for two years and actually do not show any resistance. Same for Baby Love and most “moderns”.
The Fairy or Frederic Mistral (The Children’s Rose) are interesting as they are cleaving: consistently BS resistant and other spots susceptible.
For years I was hopeless until I grew some among the latest Kordes and found their resistance both reliable and persistent. Ratings at the K site are quite realistic: here three stars is often good enough and much better than most other breeders intros.
By autumn that here begin with augustus 15 rains there is an annual and gradual resistance downgrade for some vars (not all i.e. some Teas and Chinas) as susceptibility is often temperature related.
Pierre,
Could you please list some of your more resistant Kordes roses? I’ve tried Westerland, Rugelda and Carmela Fairy Tale and their resistance broke down in my garden. I’m having much better luck with some of Bill Radler’s roses.
Many Radler’s or Lim roses are not available here so I cannot comment.
Same as you for older bred Westerland, Rugelda and not top Carmela Fairy Tale. For these Kordes rating is 3 stars for BS and PM. A bit more than deserved.
Later bred are more and more reliably rated even if some may be down graded.
For many years now K release yearly a few vars rated 4 stars for BS that are quite reliable here in very testing conditions vars like Pretty Woman cannot cope with.
Some older ones are 2007 Gebruder Grimm, 2002 Gelber Engel that I grow from introduction year.
Wedding Bells is a very fine HT I had for four years; strong and healthy as are Sunny Sky or Novalis.
And there are many more along the same line I have not tested long enough.
There are probably other valuable roses as german breeders and scientifics are working hard toward chemical free roses. With a serious fore head.
Quoted from official site: ADR (Allgemeine Deutsche Rosenneuheitenprüfung) Trials for two decennies now… main characteristics for this evaluation however are resistance to pests and diseases. The ADR varieties grown at… eleven trial sites all over Germany and for several years …are cultivated with out any chemical pesticides to evaluate their natural beauty and strength…
Pierre,
Thank you for naming a few Kordes roses that you feel are very resistant. I’m trying to find a source that has Gebruder Grimm in stock. I’d like to find Gelber Engel as well but no luck so far.
Let me insist: there are every year a few roses introduced with four stars for BS resistance Kordes rating you can rely on: they are practically immune. If every leaf may not all last spring to autumn, the plant is all along well clad with healthy leaves.
As soon as in America consider i.e. Floribunda Rose, Ground Cover Rose Bentheimer Gold ® Kordes’ Söhne 2015 four stars for black spot in a shade not unlike Caramella. Firebird, Märchenzauber, Oh Happy Day, Sweet Honey just from same batch qualify.
Airbrush is a painted desease resistant Floribunda .
I wish they could/would rate them for rust resistance. That is the primary issue growing along the California Coast.
Pierre,
Until some of the ones you mentioned are more available, I’m going to give Rugelda another try and hope that F1s are healthy.