bluedogJune 21, 2006

I'd love some advice on treating blackspot. I tried to control it organically last year and it got totally out of control. Even my disease resistant varieties have it (but are responding to treatment more than the non resistant ones). This is what I'm doing so far:

-spraying wih neem oil weekly

-collecting all diseased leaves before they fall

-keeping pruning instruments clean

-cornstarch, garlic, and bananna peels in the soil

-keeping plants fertilized with Rosetone

Should I use something stronger than Neem either instead of or in addition to it?

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mprats(z6NJ Plainfield)

All I can tell you is that blackspot hit my roses earlier this year, so I don't even want to see what things will look like in mid August.
I spray with the Cornell formula, but my attitude is that if a rose cannot survive in my garden with organic means, it will be shovel pruned and replaced with something else, even if it is a once-a-year bloomer.

My irises were also hit with rust, which had not happened before. Maybe we're having a bad year for fungal diseases...

    Bookmark   June 22, 2006 at 12:39PM
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diane_nj 6b/7a

mprats has the right idea. If you do not want to use a commercial fungicide, then get more disease resistant varieties.

If you are willing to use something other than Neem or the Cornell formula there are a few options. Bayer Advanced Disease Control for Roses, Flowers & Shrubs Concentrate has been very effective for many people, including those in souther states. It would be applied via spraying, every 10 - 14 days. It is said to be effective as both a preventive and a "contact" fungicide (kills any active BS and also helps the plant resist BS). Bonide Infuse (same active ingredient as Banner Maxx) uses a different fungicide, but also would be sprayed every 14 - 21 days (I've not gone longer than 17 days). If you have a few roses, there has been success noted with Bayer Advanced All-In-One. This is a soil drench (mix in bucket and apply around roots of rose). It is a combination fungicide, insecticide and fertilizer. Effective for 4 - 6 weeks, but takes 4 - 6 weeks to become effective. any of the above would be used instead of Neem.

As for leaf removal, if the leaf is still green, leave it on the plant. A green leaf is still a productive leaf. Once the leaf turns yellow or falls off, then it can be removed.

    Bookmark   June 22, 2006 at 2:44PM
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I am not opposed to a commercial fungicide at this point. Which of the ones you mentioned do you prefer. If I really want to kick the BS's butt, could I use the soil drench and the topical spray?

    Bookmark   June 22, 2006 at 10:02PM
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chefhick(z6 NJ)

I have been gardening organically for 20 years. I have given in on my roses though. I use the bayer fungicide through the season. For the amount of time I have to keep an eye on them I needed something more than I could find organically.

It is not that I try to control every fungal malady in my garden. I have anuals and perenials han can succome to something or other. I fertilize with Rosetone and spray with Bayer when I see spotting occuring.

I do my best to keep flower petals and leaves out of the bed and water carefully to avoid wetting the leaves. I tried once to sanatize my pruners and found it way to difficult.
I obcess enough in my life and love the release I get from getting knees dirty while working the soil.

I wish I could have the roses without the spray.

Good luck
Chef Hick

    Bookmark   June 22, 2006 at 11:26PM
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Loretta NJ Z6


I haven't been following the rose forums for the last few years. No room for more roses so why torture myself? But I remember at one time, everyone was trying Mancozeb. They applied it once every three days, 3 times to stop blackspot and then once every 10 days. Also, they were using wilt pruf after that. What happened to that?

    Bookmark   June 24, 2006 at 3:09PM
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diane_nj 6b/7a

I still use mancozeb (manzate) because I still have some left, as well as Banner Maxx, so those two are still my products of choice, and the program continues to work very well for me. Some of the folks over on the Roses Forum have tried the new Bayer Advanced Disease Control, and have said that it works in both halting active blackspot and as a preventive. I can't find it around here, I would like to try it. I guess if I had to recommend one now it would be Bayer Advanced Disease Control (not the All-In-One because I'm not fond of combination products, but do a search over on the Roses Forum, there are a LOT of threads about it).

Folks, in order to control blackspot, you can't wait until you see blackspots, you really should start spraying early in the season, and on a regular basis. If you wait until you see blackspot, you'll always be in catch-up mode. If you want to grow hybrid teas, then you will have to treat for blackspot. Or, grow roses that are blackspot resistant, there are plenty of them that do well here.

    Bookmark   June 25, 2006 at 7:45PM
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