Quite a few years ago, Jon Singer who lived in Issaquah, WA, hooked the hose up to his hot water heater and parboiled the Downey out of his roses. We laughed like idiots that it appeared to clean up the out break in his garden.
So many questions… LOL
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pH of the soil here is Acidic… between 5.5 and 6.5.
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Marks on M.I.P. coujld be black spot… though I usually see significant yellowing as well… M.I.P. get’s it all however, so probably is a mix of everything rolls eyes.
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The poppy field was an 8 photo stitch… I was thinking of removing the power poles… but I kinda like them. I teach graphic design and photography classes and publish the school yearbook every year (except this year coming… it’s just too big a job and I need a break), as well as science and maths so photochopping is no biggy… I’ve been using photoshop since photoshop 3 came out LOL. I just liked the authenticity of them
I actually do have a range of Tasmanian panoramas on coffee mugs that people can purchase 
LOL I won’t shamelessly promote them here though… not the place… -
The Ridomil was recommended to me by a local agronomist to get in with a quick kill followed up with preventitive treatments of Mancozeb and rotations of other systemic fungicides at a later date to prevent fungicide resistance occuring. I’m predicting, however, that once it warms up here a follow up with the big guns is probably not going to be needed. I’m in the process of cleaning things up so I can apply the initial dose of Ridomil. It’s a big job as the gardens cover an acre of land with mixed perennials throughout the whole thing and hundreds of roses.
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In our area the big three crops are potatoes, poppies, and pyrethrum, in this order. The idea of it being different to rose downey mildew had crossed my mind given I am surrounded by poppies, potatoes, and pyrethrum… all of which get fungus outbreaks of one description or another. This is also why I went to a local agronomist for advice.
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The conditions here have been uncharacteristically cold and wet. Days of 19 degrees tops and nights down to 5 degrees (all Celsius of course). In the last week, however, the hot weather has kicked in and I’m getting days of over 30 degrees but the nights are still quite cool (so preparing for a powdery mildew onslaught now instead
). We haven’t had any rain now for about a week and a half. The downy mildew outbreak has slowed and roses look to be making a recovery (I saved the little Test Tube Baby Love plant… which was my main concern), but I will still hit them with a dose of Ridomil. I hate it so much and this will be the first time I have sprayed anything in 5 years. I would like to hit them with hot water from the hotwater system but think the logistics of doing this over an acre (and not to mention having my lovely wife and three kids who all want showers LOL) makes it a little ‘impractcal’.
I’d test your soil mineral content too. Personally, it’d be worth the effort to see if using dolomite on the ground around a specific area helps deter future Oomycete infestations. I also think it could be beneficial to somehow get diluted, non-burning concentrations of something like calcium chloride to stick to the plants as a preventative. Likewise, the soil may also be a haven for spores, which hide from the UV that can kill the spores.
LOL…that is exactly why I started this thread…to see if the whole DM thing can be bred out in future breeding lines, and not have to go down any cultural amendments!!!
If it were my roses, I would let the DM do its thing without any control measures (painful and costly in the short term as this may prove), let it burn itself out, and use whatever roses proved unaffected for future breeding. Why, this would be no different to what a lot of us talk about in selecting out for other diseases of the rose.
Just my opinion.
LOL
George, theyre both asexual and sexual so I highly doubt it. They can not only mutate but also breed with other species.
I suppose roses that ward off the piercing parts could be created but it would be at the expense of other traits. However, as we have seen, we have come a long way away from roses as archetypal of an era and color as Golden Masterpiece.
You know, thinking back now, I’m now almost 100% certain I saw Downy Mildew on R. Fortuniana stems a few years back, but the plant was a one year old spindly rooted cutting. It died… I am so glad I just made this connection, finally!! The black patchy stem necrosis and subesequent rapid death of that little plant had me totally baffled at the time!!
Whow knows Michael, what you say is interesting too… At least we now know from what David Z posted, that breeding for DM resistance is at least something others seem to have considered, and there appears to be some proof of prinicple that it has been done with selected species X moderns.
Correct, but the dissease type is more dynamic than fungi are by far so time span becomes a huge factor. In as much as I love hybridizing, we must not forget that this is firstly horticulture. The emphasis is on the latter half here. We cannot solely rely on one factor of the whole. Also, as stated before, selecting strongly for one trait like this really limits so many other tangents. One of the major limits in there here and now that I see is that the areas not really prone to this type of pathogen are the same areas where rose species that do not get the diseases are not prevalent. This creates a multiplicity of constraints on top of constraints already in place by true fungi, among other things. Can you see my perception of this issue?
Also, what about the now? I use the Cornell mixture from time to time. Its wonderful for me on the rare occasions I use it as a preventative. What can’t we also formulate an idea in which aids in prevention of oomycete infestations? There is no reason to suffer during the time of progress.
Similarly, anything found from experimentation for actually works on this class of pathogen would be helpful in understand what to breed for since the entire class is still not understood all that well, and it still razes land for millions of dollars in damage.
Hi Michael, I totally understand that you may have a different take on how to manage DM as an amateur breeder. It looks like I am more of a cowboy when it comes to letting nature take its course +/- shovel prunung in the quest for selecting against some of the unfortunate things about some roses.
I know it’s easier said than done, but allowing it to run its course and use what’s left standing is really the only way to hope to create resistant results. I’m so thankful it hasn’t been a real issue here!
Simon wrote:
>>>>>>>>>>>>>>>>>> Clinophylla was 50% infected (which makes sense as it’s a rose from the tropics… it has no need to develop immunity to DM which is more of a problem in cooler weather), but is recovering well<<<<<<<<<<<<
By this, did you mean that 50% of your OP R.clinophylla showed signs of DM, and the other half did not?
…or did all your OP R.clinophylla seedlings develop lesions of DM, with about 50% of the plant parts affected??
One of my seedlings is experiencing disease problems.
Downey or something else? Any ideas?
All the clinophylla seedlings lost 50% of their leaves.
Hi Simon!
Thanks for the clarification.
This sounds a bit of an issue regarding Clinophylla and DM!!!
I must try and combine clinophylla with more DM resistant types. Your Anne Endt sounds a good match for this, but I don’t have it!! R.gigantea sounds great also.
BTW… A week or so ago, I asked Viru if he can possibly send me some of his OP R.gigantea, to see if we can germiante it real soon via EE/WEC.
If I get lucky, I’ll let ya know about it.