What are these spots on the canes?

kittymoonbeamJanuary 29, 2013

This Sugar Moon was healthy all year and just has a touch of rust, just a few small places but the canes look awful with purple spots. When I cut the canes I didn't see any brown wood. I wiped with alcohol between cuts. I read about downy mildew but there haven't been leaf spots or leaf drop.

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here's another picture. Should this rose be removed? I don't see it on any neighbors yet

    Bookmark   January 29, 2013 at 5:42PM
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Another spotted cane rose turned up in the back.

    Bookmark   January 29, 2013 at 5:43PM
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Another picture of the rose from the back. In both cases, no next door roses have this. Again, the leaves look pretty good but the canes are a mess. On this back rose, some canes look good, some so so and some really bad. On the front garden rose the canes all have spots but the spots aren't this dark.

    Bookmark   January 29, 2013 at 5:48PM
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Kittymoonbeam, could the spots be the aftereffects of our recent supercold weather? I don't think I'd be in a great rush to "do" anything about them, especially since you can't find anything amiss inside the cane.
Come to think of it. . . .
(Passage of time while I run outside) . . .
As I suspected, my Sugar Moon has the same spots. I'm pretty sure it's just a kiss of frost. I won't worry unless Kim or Jeri say I'm supposed to!


    Bookmark   January 29, 2013 at 5:52PM
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hoovb zone 9 sunset 23

downy mildew, sorry. :(

See the photo on this page, down almost at the very bottom of the page:

Here is a link that might be useful: downy mildew photo at bottom of page

    Bookmark   January 29, 2013 at 6:17PM
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In my reading about downy mildew, it was shown that the disease can go through the canes to the roots and so the plant will never be cured. This along with the fast spread of the disease makes me want to remove them asap and get replacements if it is downy. There was no BS on either rose so no confusion there. The semi circular planting of The Fairy surrounding Sugar Moon is completely clean.

    Bookmark   January 29, 2013 at 7:12PM
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jerijen(Zone 10)

Yup. Downy mildew.

When the disease first re-appeared years ago, we actually lost a couple of plants to it.

We tried the recommended drenches. Quit with that when it melted a plastic measuring spoon.

We next studied what Avocado growers were doing for the related Avocado Root Rot.

The eventual results of industry research pointed toward piling fresh horse manure around the trees, right out to the drip line. The idea was that the plants (trees) built up a colony of beneficial bacteria which allowed them to overcome the effects of the disease. So, that's what we did.

And it worked.

I am sure the organism remains, but it no longer manifests itself, beyond an occasional haze of purple on canes, or some marks on foliage when conditions are particularly cool/dank.


    Bookmark   January 29, 2013 at 9:05PM
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nanadollZ7 SWIdaho(Zone 7 Boise SW Idaho)

That's very interesting, Jeri. Over the years, I've noticed similar spots on some of my roses to which I paid no attention. They all went away and I never thought anymore about them. But I do use manure regularly around my roses, so perhaps that's the reason. It's nice to know there is a simple solution out there. Diane

    Bookmark   January 29, 2013 at 9:50PM
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jerijen(Zone 10)

I have been told that the fungus is out there, in the fields where roses have long been grown. Can't really be eradicated -- so I'm told.

Makes sense.

It will go dormant, in hot, dry weather -- but where I live, with no really cold temps, no really hot temps, and lots of humidity, it hangs around.

The world isn't perfect, and this is another one of those things I can't mend -- and so refuse to lose sleep over.


    Bookmark   January 29, 2013 at 10:42PM
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I was really busy this year and just had shredded trimmings to mulch with and didn't go to the stables like I usually would. Add in the cold wet weather and I guess it makes sense. Sugar Moon is right out in front too. Great all day sun and perfect air circulation. Nothing near it except a low planting of The Fairy. Oh poop. In all other regards it was a great rose for me. The so. CA fruit tree folks are forecasting another cool wet spring so I'll have to be extra watchful.

    Bookmark   January 29, 2013 at 10:54PM
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michaelg(7a NC Mts)

There are many different fungi that can cause spotting of green canes. including downy mildew, blackspot, various cankers, and relatively harmless fungi. I can find spots like that in my humid garden just about any time. I've learned not to worry about it.

I don't want to argue with Hoov and Jeri, since they are expert Southern California growers. But if you are not seeing angular spots on new growth and having leaf drop, I would not assume it is downy mildew, and I certainly would not destroy the plants--just remove the badly affected canes and wait and see.

    Bookmark   January 30, 2013 at 10:42AM
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jerijen(Zone 10)

But if you lived in Southern California, and had experienced the weather conditions we've had in the past couple of months, and you knew how widely-spread this fungus is here (and has been for some years now) you likely WOULD assume it to be downy mildew.

And, no, I would not destroy the plants. Your replacements will probably also have it, and the problem will not manifest itself once the weather becomes warmer and drier.


    Bookmark   January 30, 2013 at 12:35PM
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Thank all of you so much for this thread, and especially hoovb for providing more info! In reading this I just realized that I have DM in my garden. We are cool and very wet all WInter, as it is our rainy season. So, I guess it is not a surprise.

Are some cultivars of roses more susceptible than others? I have seen these spots on roses from time to time, but nothing much else happened. However, I now realize in retrospect that this must be the disease that killed not one, not two, but three very large mature bushes of 'Le Vesuve' (including one that was almost 100 years old) in my garden. All of the descriptions are spot on, especially the speed of the progress of it, and that it starts at the tips of canes and works its way down to the roots. The last LV that it killed was only about 8 years old. We noticed that the top & edges of it were dying, and I cut off all of the canes below the bad parts, to no avail as it turned out - the entire thing was dead dead within a few days. I had sprayed it with Funginex and the Bayer fungicide product, which one of the articles I found said will do nothing for DM, and they did nothing.

So, luckily I have a 2 year old healthy, clean 'Le Vesuve" (which I had rooted from the old ones) in a pot in the other end of the garden. I was planning on planting it where the last one died (I had already planted 3 other roses where the first 2 LVs had grown, and this morning I noticed that one of them, Lady Hillingdon, appears to have DM too).

So, I will now try and root new plants from my last remaining Le Vesuve prior to planting it in the garden, and I will get some horrible poisons as recommended, and spray the little Lady Hillingdon and the roses around it. The articles said to cut an infected plant way back after conditions have improved, but here the temps will not be over 80 degrees for several months, and we have at least 3 more months to go in our rainy season.

So, is there anything else I should be doing, other than normal pruning and care of the rest of my roses? The articles I read implied that DM does not necessarily or usually kill rose bushes, but it sure killed all 3 of my Le Vesuves quite promptly. A heart breaker, as you can see from this pic - it is of what turned out to be the two, not one, original bush (when we dug it up because it was dead, we found that one half of it was a new bush - it had tip rooted itself at some time in the past - the cane linking the two bushes was still intact).


    Bookmark   January 30, 2013 at 5:01PM
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jerijen(Zone 10)

Jackie -- When DM hit the Southern CA rose community years ago, we lost one or two roses.

That speared us to try the chemical drenches recommended for control of the fungus. But we QUICKLY realized that we weren't going to continue that. (Chemicals that melt plastic, after all, are not welcome here.)

We next tried the avocado farmers treatment, and spread fresh horse manure around the base of the roses, and watered that in.

The roses began to grow strongly, and put out new growth. Signs of the fungus were reduced to minimal levels.

It has appeared to me, over the years, that the roses so treated were left with increased resistance to the fungus, because we have not been troubled with it, since.

Not sayin' you have to do likewise, and there may be other viable approaches, but fresh horse apparently worked for the avocado farmers, and it worked for us.


    Bookmark   January 30, 2013 at 5:44PM
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This morning I looked everything over closely in the morning sun. I decided to shovel prune the two spotted roses so they won't spread the disease. If I only see it on a few more then I'll just remove them. These are easy to get HTs. I hope to slow it down and maybe it won't get on my big antiques I grew from bands. I'm willing to lose a few easily replaced HTs to try to contain this disease or slow it down. I cleaned up and put down new mulch. Hopefully this weekend I can get some manure and won't be seeing spots anymore. It's probably in the soil now don't you think?

    Bookmark   January 30, 2013 at 6:24PM
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Rosemania sells something called Actinovate that it says is just a concentrate of beneficial bacteria, which when diluted is recommended for all sorts of fungal problems on roses including Downey Mildew. Sounds like the same basic theory as the fresh horse manure. Anyone have any experience with it?


    Bookmark   January 30, 2013 at 6:40PM
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Actinovate has been around for a few years and is pretty expensive and supposedly will work wonders for a lot of diseases.

It's available at most of the local nurseries here where I am.

Here is a link that might be useful: Actinovate

    Bookmark   January 30, 2013 at 9:07PM
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jerijen(Zone 10)

I'm not familiar with it, Jackie -- but I agree that it sounds like a high-tech variant on the same idea. I hope it works. :-)


    Bookmark   January 30, 2013 at 11:19PM
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