Will BS kill my roses?

melian1212October 23, 2012

I'm pretty new to gardening and have decided to go organic from the start...I have had some roses for 3 years and this year I have not sprayed for BS or others... There is an outbreak right now and I don't know what to do...Will I be able not to spray? Or will I loose the plant in the end? Thats my only fear, that if a don�t do anything the plant will eventually die... I don�t mind loosing a couple or replacing them if they are not performing that well but...not all of them...Do plants resist continuous fungal attacks? I'm hoping that the higher temperatures will stop it before they are defolieted but I don't know if I'm right...

I would appreciatte your opinion! I have learnt a lot reading the forum and would love to continue doing so!


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In my experience blackspot does not hurt roses. The roses defoliate in my no-spray garden setting, however they grow well and bloom well. Blackspot does not diminish vigor or hardiness.

I've found that organic fertilizers build the soil to create an environment where roses thrive, even with blackspot present in the garden.

    Bookmark   October 27, 2012 at 8:09PM
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Thank you so much for your answer Krista! You give me hope! Right now my Graham Thomas is practicaly defolieted and almost all the roses have blackspot... So I suppose that what I should do is to hide them among other plants so I can enjoy the flowers and not see the leafless bushes... I think thats what I will do!

Thanks again


    Bookmark   October 29, 2012 at 2:46PM
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Try using Serenade it is an organic treatment that has worked well for me.
I dose heavily, far beyond printed doses.

Some roses are tough and will not die but others will die as the black-spot is as hard on some roses as some diseases are on people.

If you let it go uncontrolled you wil severly limit your choice of roses in the future.

High tempuratures will make it worse, far worse.
My one garden this year had none until the dry and heat hit Minn.
In the worst of the near drought was the worst of the black-spot.

    Bookmark   November 6, 2012 at 12:06PM
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Melian, I didn't mention in my previous post that I grow a wide variety of roses: Austins, old and modern Hybrid Teas, antique and modern shrubs. They do fine with blackspot. Gardening without spraying has not put restrictions on the types of roses I'm able to grow.

I use summer annuals to brighten the garden when the roses have dropped their leaves.

    Bookmark   November 8, 2012 at 5:54PM
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It is bizzare to suggest to any one not to treat roses because-- supposedly-- it has not hurt yours, because you fix the problem by hiding it.
If you have never lost a hybrid tea you are a god among rose growers.

I grow mostly hybrid teas and black-spot untreated DOES have effect on how they do the following year.

I have tried letting it go in the far past.

I have other non-hybrid tea roses and some, beyond trimming out bad sections, occasional spraying to STOP SPREAD and picking bad sections, it does not seem to bother them much but I finally moved them to an area where the cannot infect the hybrid-tea roses.

Here are what those whose career deals with black-spot problems have to say about treating and possible harm.



    Bookmark   November 12, 2012 at 10:21PM
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strawchicago(zone 5a)

I second what Krista said. She grows several hundred roses with over a decade of experience. The below link lists the varieties of roses that Krista grows.

I have 42 varieties of roses, I don't spray, with very few have minor blackspots. The retired chemistry professor Henry Kusha documented a few studies that show chemical spray eliminated beneficial bacteria that suppress fungal growth. There's a British paper on using horse manure as mulch as effective in a no-spray rose garden. Horse manure has lime, a natural fungicide. I'm next to a limestone quarry, with alkaline clay, and many of my roses are 100% free of blackspots .. so what Krista wrote about her no-spray, no-kill garden is true.

Fifteen years ago, in my last house, in an acidic soil environment, I had the WOSRT BLACKSPOTS even with chemical spray. There are different soil chemical compositions and different organisms in different garden, thus different results.

This is how my roses look like, pic. taken in October during our wet fall, end-of-season.

Here is a link that might be useful: List of roses that Krista grows for the past decade

    Bookmark   November 27, 2012 at 2:30PM
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strawchicago(zone 5a)

Melian, I re-read what you post: 3 years of little BS, until the 3rd year that it hits hard. It's typical for roses to get huge the 3rd year, and break out in diseases due to both lack of air circulation and not enough water to support the massive growth. Hard pruning will help to cut off the diseased part, and to keep roses small, thus less demand on water.

I'm in zone 5a, where winter-kill to the crown is blessing. University of Illinois recommended pruning drastically to a few inches, so that the new growth will be free of BS in the spring. The advantage of horse manure over bark mulch are: 1) lime in the manure is a natural fungicide 2) horse manure has beneficial bacteria that suppress fungal growth 3) horse manure dries off fast, versus wet bark mulch that foster fungal growth.

At least 20 of my roses are in their 2nd year, still zero blackspots. Winter-kill in zone 5a keep my roses really small, and new shoots in spring have plenty of vigor and water to fight off any diseases. How much diseases you have is dependent on how much potassium in your soil. Potassium is needed to fight diseases, strong stems, and bloom production. It's worth it to have your soil tested at $20 by EarthCo., county extension, or University extension to see if your soil is deficient in potassium. The remedy? Sulphate of potash, less chemical fertilizer (salt in chemicals drive down potassium). My soil is tested a tiny bit deficient in potassium, that's why I use organic fertilizer like manure and alfalfa meal to avoid the salt that drives down potassium in soil.

    Bookmark   November 27, 2012 at 2:50PM
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Serenade is not a chemical spray.

I do not know why one would do it but you could drink it and it would not hurt you.

    Bookmark   December 17, 2012 at 7:50PM
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I live with extreme disease pressure with heat and humidity year round. I have been 100% organic, no spray for a year and just in this one year I probably lost 1/4 of my 50 roses to black spot. I have very fortified soil, alfalfa, fish fertilizer, etc. The soil is rich and healthy. I am replacing with old roses. Modern roses here without spray is just going to continue to break my heart.

    Bookmark   December 31, 2012 at 4:31PM
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The following reviewed recent scientific paper may be of interest.

Here is a link that might be useful: 2012 scientific paper

    Bookmark   January 4, 2013 at 4:01PM
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