Black Spot

forflowers(9a)March 19, 2005

I'm looking for advice from other organic rose growers in Florida Zone 9. What do you do for black spot? I have tried skim milk, Organicide and baking soda with 'spotty' results. Does anyone have any specific methods that work pretty well? I really want to get off Funginex!

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Sophie Wheeler

If you really want to grow roses without spraying in Florida, you're going to have to change the type of roses you grow. Modern roses won't do. Say goodbye to the hybrid teas and hello to the antique teas, chinas, noisettes, polyanthas, and hybrid musks. The folkloric kitchen sink remedies are mostly myth for areas with long growing seasons and high disease pressure like the South. If you are willing to spray all of that other stuff that doesn't work, then check out all of the modern fungicides that you can spray and DO work and will give wonderful disease control and are not nearly as toxic as Funginex. Please visit the regular rose forum for advice on that subject. But if you wish to give up manmade chemicals entirely and forgo spraying, then choose different roses.

    Bookmark   March 20, 2005 at 9:43AM
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Kimmsr(4a/5b-MI)

Both a spray made of a 50/50 mix of fat free milk and water sprayed every 5 days and 1 teaspoon of baking soda with a few drops of a light oil mixed in 1 quart of water and sprayed every 5 days have controlled black spot for me on some nursery stock I got that had it.
Since we only have fat free I have not used skim milk and they are apparently different since the stores have both.

    Bookmark   March 21, 2005 at 7:07AM
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ejillparker(z7OK)

Well, I am not in Florida but I live in central Oklahoma where it gets very humid in the summer. I grow hybrid teas, which everyone knows, are magnets for BS. I use a mixture of 1 tablespoon of white distilled vinegar (the kind from the grocery store) per quart of water sprayed on the foliage. It works pretty well. I think the small amount of acid in the mixture is just enough to keep the ph at a level in which the fungus that causes BS cannot thrive but yet it is small enough an amount so as not to burn the leaves. Hope this helps.

    Bookmark   March 21, 2005 at 9:04PM
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Sophie Wheeler

Black spot in a 120 day growing season where the heat zone is 3 or 4 and the humidity is 60% is a totally different experience than where you have a growing season of 300+ days, the heat zone averages a 9+, and the humidity levels are 90-100%. Very few black spot spores overwinter on dead canes, whereas they thrive year round on 7' ladder climbers in the South. Judge the total disease pressure of your particular climate when judging whether or not something that is reported to work in another location will likely to be effective in yours.

A shovel works 100% of the time to eradicate disease from any garden, regardless of location.

    Bookmark   March 22, 2005 at 8:34PM
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JenniferSomogyi(7)

I had black spot on my Roses a while back, and found that nothing was working to clear it up. I finally cut off all the leaves that had the black spot on them. Eventually trimming them back on a daily basis helped to keep it from spreading. I also made sure I watered the base of the plant, and didn't touch th eleaves, as I heard (emphasis on heard) that black spot spreads when water splashes on the leaf it is on, onto another leaf.

    Bookmark   March 23, 2005 at 12:02PM
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threeducks(z5-MI)

Both a spray made of a 50/50 mix of fat free milk and water sprayed every 5 days and 1 teaspoon of baking soda with a few drops of a light oil mixed in 1 quart of water and sprayed every 5 days have controlled black spot for me on some nursery stock I got that had it.
Since we only have fat free I have not used skim milk and they are apparently different since the stores have both.

What roses do you grow that this works on?

    Bookmark   March 24, 2005 at 9:38PM
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Kimmsr(4a/5b-MI)

"Queen Elizabeth", "Abraham Lincoln", "Peace", and some 20 others I can't recall the names of off hand. One I bought, form a reputable nursery, last year and did not show signs of BS at the nursery blossomsed with it 2 days after getting planted here and the milk/water spray cured the problem in 2 weeks.

    Bookmark   March 25, 2005 at 7:38AM
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threeducks(z5-MI)

I don't mean to be arguementative, but my mother has been growing Queen Elizabeth no-spray in mid-Michigan for years and hasn't had any trouble with blackspot (at least on that rose).

    Bookmark   March 25, 2005 at 7:40PM
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Kimmsr(4a/5b-MI)

Rarely, but it does show. Everything I find on Queen Elizabeth says it does get Black Spot, easily, and I would not have it if wife did not want it.

    Bookmark   March 28, 2005 at 4:54PM
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Patricia43(z8 AL)

You are wasting your time and money with that Cornell concoction in the south if you grow hybrid teas or Austin roses. The only roses that might even help are the ones that do not need it anyway: The teas, Chinas, Noisettes, polyanthas.

    Bookmark   March 30, 2005 at 6:42AM
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destany

Not to hijack someone elses thread, but I sorta goofed up and planted two hybrid teas next to my garden pond. They're healthy now, but I don't want to wait until a flareup of blackspot before running to you guys to help fix it;^)
Will the nofat milk and water with bakingsoda and oil work well on Kordes Perfecta and Blue Girl in the Midwest? Is it safe to use next to goldfish?
Is there anything else you would recommend instead?

    Bookmark   April 16, 2005 at 10:26AM
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henry_kuska

Title: Biological control of black spot of rose caused by Dipocarpon rosae .
Authors: Prasad, R. D.; Rangeshwaran, R.; Sunanda, C. R.; Vinita, J.

Authors affiliation: Project Directorate of Biological Control, Post Bag No. 2491, H.A. Farm Post, Bellary Road, Hebbal, Bangalore 560 024, India.

Published in: Annals of Plant Protection Sciences,volumn 10, pages 256-259, (2002).

Abstract: "Fungal biological control agents (Trichoderma harzianum , T. viride and Chaetomium globosum ) were used either alone or in combination with fungicides (chlorothalonil and mancozeb) to manage black spot of rose caused by D. rosae under greenhouse conditions. Black spot incidence in biological control agent and/or fungicide treatments was significantly low (disease ratings from 0.33 to 3.33) compared to the control at all observation dates. After 100 days of spraying, defoliation was lowest with chiorothalonil, Trichoderma harzianum +chlorothalonil, C. globosum +chlorothalonil and T. harzianum +mancozeb treatments. The highest mean vigour index was recorded in T. harzianum treatment. The highest flower production was recorded in C. globosum +chlorothalonil treatment (4.33) followed by T. harzianum alone and T. harzianum +chlorothalonil treatment (4.00)."

    Bookmark   April 16, 2005 at 12:37PM
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bugbite(z9a FL)

I also tryed Vinegar...
I soaked $4 worth of pennies in a quart of vinegar, since January. Did not use it until last week. I had one rose that was getting blackspot so bad that leaves were dropping fast. I also put a little over a tablespoon in a quart of water. I chose this amount because it got my alkaline water to a PH of about 5.5.
I sprayed the soil in the pot where the rose is growing and the rose. I left specks of Blackspot on some leaves. All blackspot has halted and the rose and new grow seems to have perked up.
If you try this method, experiment on one rose or part of a rose. I will not know if I recommend this approach until I do further testing.
Bob

    Bookmark   April 24, 2005 at 11:37PM
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Xochitl10(z7a MD)

I sprayed with the vinegar/water/soap mixture last weekend (and mid-week, after a rain), and the blackspot on Glamis Castle and Mystic Meidiland appears to be halted. Will the spots that were on the leaves prior to spraying disappear, or will they always be there?

Thanks,
Xochitl10

    Bookmark   May 1, 2005 at 12:03PM
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JAYK(8b)

Once a leaf is infected with blackspot, its appearance will not be affected by any spray or treatment.

    Bookmark   May 1, 2005 at 2:35PM
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ramblinrosez7b(JerseyShore)

Orthinex RosePride works good, just make sure you wear a space suit, goggles, gloves and a surgical mask. Oh yes, make sure you don't forget to wave hi to your neighbors.

    Bookmark   May 6, 2005 at 9:27PM
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sharons2(z3-4 ID)

Is this BlackSpot?

Would baking soda work on it? Or non-fat powdered milk that has been rehydrated? (We buy whole milk. Would it not work?)

Or how much dish soap? I'm leery of the dish soap trick since I tried spraying soapy water on a miniature rose once and a lot of the leaves then fell off. Then I fertilized it with some rose fertilizer, and that killed it completely.

Thanks,
Sharon

Here is a link that might be useful:

    Bookmark   June 4, 2005 at 12:29PM
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Sophie Wheeler

It looks like the beginnings of black spot, but the photo really isn't clear enough. Black spot can only be prevented not cured. If you start spraying now, the new leaves will be protected. None of the BS things you list will work at all on BS. If you choose to use organic means of control, horticultural sulpher is the most effective choice, at approximately 40% control in my trial. It can burn foliage in heat. Never mix it with any oil treatment any closer than a couple of weeks apart. The two combined will fry your foliage. As has been said, the most effective organic black spot control is your shovel and your willingness to use it to remove prime offenders from your garden. That's a 100% cure.

There are plenty of fungicides that are discussed on the regular rose forum that also provide close to 98% control if you should decide to try to keep the plants you already have and want better control than organic means can provide.

    Bookmark   June 5, 2005 at 9:17AM
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lavenderkitty(7aNC)

I have BS on my hybrid teas and The Fairy (if you can believe that). I sprayed them with Safer's Sulfur spray. Now the plants actually look worse!! The leaves are all yellow. It was not hot the day I sprayed, and I thought I had watered well. Now I am afraid to use the stuff again.
Any suggestions??

    Bookmark   November 5, 2005 at 1:09PM
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Victoria(Jax,Fla)

I used the Cornell spray on six sad roses ( Peace, Mr. Lincoln, Blanche ??) and it worked. Or something worked. They were black and bald after the third hurricance last year and now I have blooms that I can cut and decorate my B&B.

    Bookmark   November 7, 2005 at 10:28PM
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diane_nj 6b/7a

lavenderkitty, by the time you saw the blackspot, the disease had already taken hold. It wasn't the Safer's. The key to BS prevention is a regular program of spray, not just attempting to "cure" the disease when you see it. By the time you see it, it's too late, and now you are in the mode of attempting to halt it's spread.

    Bookmark   November 9, 2005 at 9:24AM
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dandyliondancer

Organicide seems to be an oil spray, which isn't particularly effective on blackspot from what ive read. i cant vouch for the effectiveness of other organic controls, but a list can be found at ATTRA:

http://www.attra.org/attra-pub/biorationals/biorationals_results.php?PestType=Disease&Pest=Black+Spot&TradeName=&ActIngred=&Go=Search+Treatment+Options

note: copper and sulfur sprays can be damaging to rose foliage under certain conditions

    Bookmark   November 25, 2008 at 1:50PM
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novice_2009(zone 6b)

I'm struggling with a rosebush and the blackspot is out of control. I pruned and removed leaves affected, and it still spread. It really is out of contol- love to take s shovel to it but it's a house i'm renting. I don't want to use any chemical spray. So baking soda spray? Vinegar? A solution of nonfat milk? Do I remove affected foilage first? How long to spray? And yes- it's hot and humid here. What doesn't help is the rose is right against the front of the house, not gutters there! PLEASE HELP!

    Bookmark   April 26, 2009 at 1:35PM
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Lalakids2000_yahoo_com

Will the milk and water work? Also do you do this with the oil ,baking soda,and water mixure together with the milk mixure as well? My roses are so pretty and I work hard to keep them looking great. Just hate to see the black spots..why does this happen ? Thx for your help

    Bookmark   May 31, 2011 at 11:13PM
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