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Cercospora

Posted: Thu Aug 02, 2018 2:03 pm
by dgermeys
Does anyone has experience with roses that are resistant to cercospora? I know there have been discussions about this disease but maybe an update on this information could be interesting.
Or if you know species that are resistant, that would also be interesting!

Re: Cercospora

Posted: Thu Aug 02, 2018 8:47 pm
by david zlesak
I don't know of any roses in my garden that don't get any cercospora. Many rugosas seem relatively clean of it. I was in a non-sprayed garden today and Screaming Neon Red seems to have a lot less of it than a lot of other roses. I have some op seedlings of Rainbow Knock Out that seem to be relatively clean of it. RKO gets a good amount of cercospora for me (other Knock Outs are much much cleaner). I'm not sure what the male parents were, but the seedlings are one time bloomers. I suspect the dad(s) are some roses with Explorer climber blood in them ('John Cabot', etc.). Explorers (the non 100% rugosa ones) generally get a good amount of cercospora in my garden. I wonder if there are different resistant genes from each of the different parents that when by themselves were overcome by the races in my garden, but with both resistance genes together in a single rose, there isn't a race that can easily overcome both together in these seedlings? It is just a guess.

Re: Cercospora

Posted: Fri Aug 03, 2018 9:00 am
by Rob Byrnes
Off the top of my head, these are pretty clean of cercospora so far this season: Morning Magic, Cape Diamond, Quadra, Canadian Shield, Top Gun, "Fire'n Spice", Basye's Blueberry, 'Red Dawn x Suzanne', Thor, and Campfire.

I have a number of seedlings out of Morning Magic that show a very high resistance to BS and cerospora. Some of them don't bloom the first season and I'm wondering if that is due to the R. rugosa 'alba' blood in Morning Magic. R. glauca, and R. woodsii 'Kimberly' are not immune. I have some R. nitida hybrids that show good resistance. Metis and Orantida to be specific. 'Skinner's Red Leaf Perpetual' (R. glauca hybrid) has very good resistance.

I'm sure there are a couple that I can't remember.

Re: Cercospora

Posted: Fri Aug 03, 2018 10:03 am
by jbergeson
Julie Overom says cercospora is her number one problem. Almost all roses get it eventually. David's first sentence is stunning, "I don't know of any roses in my garden that don't get any cercospora."

So although I have many roses that seem clean, I know my cercospora pressure isn't as high. I do know I have it. Last year I planted several John Davis in my trial area to act both as indicators and incubators for cercospora. So far this year they are still totally clean, so I know that I can't get too excited about any of my other roses that are still clean.

It sounds like the best we can do is to develop and find roses that tolerate the disease without losing many leaves or becoming significantly discolored. I know my R. nitida specimen seems to get cercospora all over but it never has leaves turn yellow or drop off and still looks good overall.

I'm not sure if I've seen cercospora on pure R. carolina and R. virginiana. Julie has told me that while her R. virginiana itself is healthy, its seedlings seem susceptible.

Re: Cercospora

Posted: Fri Aug 03, 2018 12:03 pm
by Rob Byrnes
Joe,

FIVI3 is very healthy here. Getting healthy F1 is proving to be a challenge but I will continue using it.

Re: Cercospora

Posted: Fri Aug 03, 2018 9:04 pm
by srpshoy
Roemer's Hip Happy is also very clean here in GA. Maybe also Miracle on the Hudson & Poseidon.
Stephen

Re: Cercospora

Posted: Sun Aug 05, 2018 5:49 am
by dgermeys
My rosa carolina seems to get it, but just a little

Re: Cercospora

Posted: Tue Aug 07, 2018 11:16 pm
by jriekstins
Cercospora is funny. Some years almost everything gets it, esp. late in the yr. So far this yr, haven't seen a trace on anything. It has been very hot and since I am watering extra, I am taking care to fertilize extra. I have noticed that cercospora is very exploitative of low or unbalanced nutrients.

Re: Cercospora

Posted: Wed Jun 26, 2019 12:17 pm
by dgermeys
Does anyone know of botanical roses that don't get it, or only get it a little bit?