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| There is a thread concerning OGR black spot resistance on the Rose Hybridizers Association. Dr. David Zelsak, who has created and introduced several quite disease and cold resistant roses of his own and is on the "front line" in the quest for black spot research, has posted a list of roses he audited from the Minnesota Landscape Arboretum for disease. He and one of the other members are working on the Excel file to be able to post the results better, but there is a jpg in his post, providing his results after testing a number of varieties hardy in that location against anthracnose, black spot and powdery mildew. His results are likely most applicable to that area, but they demonstrate quite interestingly how resistance varies greatly between varieties. I thought some here might find the results interesting and useful. Clicking on the jpg in his results post will permit you to enlarge it. Kim |
Here is a link that might be useful: Rose Disease Ratings
Follow-Up Postings:
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- Posted by PortlandMysteryRose 8 (My Page) on Wed, Jun 11, 14 at 13:17
| That is interesting data. Most of the rugosas seem to be very clean (0 disease across the board) along with good ol' Madame Plantier. I wish one of the universities around here would perform a similar study. I'm going to reread the results when I'm back at my computer. My iPad cuts off half the page. Carol |
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| Unfortunately, the jpg cuts off half the page, so don't blame your iPad. That's what they're working on so they can (hopefully) post the Excel file, making all the information more easily available. Kim |
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| Although one expects regional differences, I didn't find any surprises among the roses I have grown. Among those I have not grown, I was surprised at the extent of blackspot on these varieties usually classed as gallica or alba (not "pure" if there is such a thing) Belle Isis |
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| Thank you Kim. Very interesting, and I hope to see the whole document soon. I wonder if the diseases act the same here as in Minnesota since our conditions are rather different? Blackspot pressure here in SoCal is pretty low, and I've only rarely seen any of my roses afflicted (observed on a few tea roses, chinas, and hybrid teas only in my garden). The one rose I had heard was a blackspot magnet, and I feared the worst, is R. foetida Persiana. Nope, absolutely clean leaves here, but the blackspot column is chopped off for this rose on the report. I'm curious how it fared in Minnesota conditions. As to mildew, well, I don't know if anywhere can top my area for high pressure, yet the Minnesota results don't always correlate with mine. One of the worst mildewers here is the rugosa Mme Georges Bruant (0% on this report), similar to its tea parent Mme de Sombrueil (that is if the rose, formerly known as La Biche, in commerce in the US is the real one). It is my only rugosa that mildews, and it is really bad. This rose also is highly susceptible to rust, something not shown on the report. Melissa |
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| That's a tease! It does make me think I should think about yanking Madame Hardy and replace her with Mme Plantier--I hadn't realized they were so similar looking. Although I want to wait and get a really, really good picture of "damasks crud" in another month or so. I'm sure M. Hardy won't disappoint on that score! |
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| Yes, disease pressures as well as which of the five main races of US black spot you have where you live are some of the reasons I stated his observations are most likely the most relevant to his climate/area, Melissa. In MANY cases, I've been able to mitigate mildew here simply by increasing the amount of water the individual plant receives. Mildew is tremendously easy to force by keeping the plant too dry. I'm seeing similar results with rust. Just give that one more water and very often, the rust subsides. Of course, that is most applicable to our climate types due to the aridity and lack of ground water, but I've heard from folks in other climates to whom I'd made the suggestion that it's working elsewhere, too. It's often that lack of humidity here that helps keep black spot to a minimum, though after our warmer, wetter winter periods, black spot is rampant in my garden. Air circulation isn't the culprit, either, as there is NOTHING preventing free air flow on this hill. Any breeze possible makes a direct bee line across here. I'm not surprised your Mme. Georges Bruant has such issues with rust and mildew. In MANY cases, Rugosa hybrids are just not suitable for much of Southern California. I gave up on most of them many years ago due to rampant rust issues which could not be prevented. Conrad Ferdinand Meyer was horrible for rust, as have been all of his close descendants I've grown. I loved Tamora, but couldn't keep the rust off her, though a budded Arena plant, supposedly created from VI material, I gave to a friend in West Hills years ago, remains absolutely unaffected by anything. The Perdita (also an Arena plant from reportedly cleaned material) beside it is unaffected by any diseases. No chemical intervention is practiced in that garden. A number of species hybrids are easily afflicted with rust. There are only a few of Ralph Moore's Bracteata hybrids which don't rust severely here. Only one of the Canadian Arkansana hybrids I've grown didn't rust at all. The clean Rugosa hybrids I have been able to grow here have mostly been Moore seedlings, though not all of his Rugosa crosses have been healthy for me. White Surprise was bullet proof, but RAMPANT and IMMORTAL. I don't generally fool with Rugosa hybrid pollen because of rust, though a few of Mr. Moore's hybrid Rugosa seedlings are producing some fairly healthy seedlings. It just illustrates how something so perfectly climate suitable in one area can be so totally unsuitable elsewhere, even when there are fairly shot distances between locations. Look at the striking differences between how many things grew for years for me in Newhall, and then here in Encino, and how they perform for you. Seemingly similar conditions (Newhall and your area), with some amazingly different performances. (Pure Bea is still happy, BTW. Thank you!) Kim |
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| Well, this is interesting information but some of it is contrary to observations I've made in this location so I guess the location and/or blackspot strains vary a great deal. For instance, Duchess de Montebello and Konigen Von Danemark are very clean here and Golden Wings defoliates to such a considerable extent I lost it this past winter after it had lost vigor. |
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- Posted by PortlandMysteryRose 8 (My Page) on Wed, Jun 11, 14 at 18:10
| The report contained some surprising info for me, too. Without spraying, when I lived in MN I healthily grew a few of the OGRs which suffered a bit in the test garden. Maybe I wasn't as neglectful as I remember. :-) Kim, thank you for the heads up about the Excel document. Carol |
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| You're welcome Carol. I hope they can get it to work. Some forums won't permit posting various types of files. Kim |
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