Roses forum→Another discussion (sorry) about eradicating black spot

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Name: Dennis Brown
The Big Island, Hawaii
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kohala
Mar 21, 2020 11:36 PM CST
I have read all of the posts on the Rose Forum I could find and the remedies suggested were all over the map. Over the past six months I have tried the following:
sodium bicarbonate (burns leaves)
Rose Shield
potassium bicarbonate
liquid copper
Green Cure (expensive sodium bicarbonate)
Serenade
mancozeb
Paul Zimmerman recommends sulphur( I haven't tried this)
None of these has worked. Some of the more seasoned veterans of the black spot wars suggest doing nothing.

Is the best "remedy" to simply do nothing?

Name: Carol
Alberta, Canada (Zone 3b)
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Canadian_Rose
Mar 22, 2020 1:26 AM CST
I'm not the best to advise since blackspot is a rarity here. That's why I have done the "get rid of the rose" if it blackspots option. That probably isn't an option for you...but I'm interested in what others say.
Name: Ken Wilkinson
N.E. GA. (Cornelia) (Zone 7b)
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KenNEGA
Mar 22, 2020 10:54 AM CST
Here we go. I have to much time and $$$ invested into growing the roses that I enjoy. Thus I invest about an hour or so every two weeks to keep my foliage in good shape. I use Bayer Disease Control. I mix Mancozeb every couple of months. It works for me.
It's a rose!!! It has nothing to do with life and death.
Name: Mike
Long Beach, Ca.
Charter ATP Member I was one of the first 300 contributors to the plant database! Roses Region: California Hummingbirder Farmer
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Calsurf73
Mar 22, 2020 11:10 AM CST
It seems to me that being in Hawaii you are in a prime climate for roses developing black spot based on the high humidity.
Maybe try picking off the infected foliage ?
Minnesota (Zone 3b)
RpR
Mar 22, 2020 7:16 PM CST
You have to remove as much of the infected foliage as you can BEFORE you do any thing.
If you use Seranade, Actinovate, Oxidate etc., or any thing similar unless the disease is removed, or treated in the surrounding ground , as much as possible , it is just laying there waiting to re-establish itself.

In wet weather , once you have it, you must treat it repeatedly, often, as you are doing a holding pattern rather than eliminating it.
I have winter here that helps control, as when I uncover the roses, I can rake or vacuum away any debris and treat the roses before leaves form.
If you leave it, especially in wet climates, you are feeding it, as it splashes up from the infested debris on the ground, which is why I often douse the area around the roses with gallons of Serenade or something similar.

I had none in one garden last summer but that does not mean I do not have to treat the garden.
If it looks like it is gone and you stop treating, you will , most likely , be in for a unhappy surprise when you least expect it.
Name: SoCal
Orange County (Zone 10a)
Lazy Gardener
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SoCalGardenNut
Mar 22, 2020 7:45 PM CST
I don't have anymore BS and it's been raining here. The one rose that might have it Grandmoter's hat. I did pick some infected leaves but that's it. Didn't spray anything. I'm kind of lazy and nature takes care of itself.
I try to grow everything, sometime not successful.
[Last edited by SoCalGardenNut - Mar 22, 2020 7:48 PM (+)]
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Name: Lola
Tasmania
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LolaTasmania
Mar 22, 2020 10:12 PM CST
When I first bought the roses for my rose border I didn't give any thought to possible diseases because I figured that as the National Rose Garden was close by I must have a good climate for roses. Not so. When a friend discovered I had bought mainly David Austin roses she said I must love spraying because I wouldn't have made that choice otherwise. She was right. I sprayed the first year and kept the BS at bay but this year I couldn't be bothered and let the roses sort themselves out. One or two are just naked and sad so they will go, but the rest aren't that bad. I grow them for the blooms - not the leaves, so I don't care if they aren't green and leafy all the way to the ground. I spray when the leaves first appear in spring and leave them alone afterwards.
Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Mar 24, 2020 6:11 AM CST
I was told by a horticulturist that spraying the ground under the roses was essential, no matter what kind of fungicide you use. She also recommended that in early spring remove all the mulch underneath the roses and spray with dormant oil at that time. Put down new mulch. As soon as the roses leaf out, if not using a systemic product, spray weekly even if you see no spots on the leaves, and spray the mulch underneath. Also change the fungicide type every two years or so. All of my roses have black spot, but following these instructions I have managed to keep it from defoliating all of my shrubs. I've been told that once your roses get blackspot, you never completely eradicate it, you're just keeping it at bay and preventing it from killing your roses; yes, it can eventually kill them by continually defoliating them, thus weakening them so severely that they can die. I've lost two because of this.
“ Be kind whenever possible”
14th Dalai Lama
Name: seil
St Clair Shores, MI (Zone 6a)
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seilMI
Mar 24, 2020 2:25 PM CST
True, Lynda. Spraying the ground helps and spraying BEFORE you see spots is vital. Once the leave begin to show symptoms by spotting the plant is already diseased. Spraying then will only keep the new leaves from further infection. Any leaves already infected, even if they have no spots yet, will continue to spot. That's why sometimes it seems your plant gets worse right after you spray. Those leaves were already infected before you sprayed and just continued to show the signs after the spray. No spray on the market is a "cure". They are only preventives for new growth.
Name: SoCal
Orange County (Zone 10a)
Lazy Gardener
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SoCalGardenNut
Mar 24, 2020 2:26 PM CST
I removed the leaves with BS today, but I didn't see any problem on new leaves yet.
I try to grow everything, sometime not successful.
Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Mar 24, 2020 2:40 PM CST
It's been raining non stop for days. We will finally get some dry weather, so I will be spraying my roses again. They've already been sprayed two times. We had very early growth on them this year.
“ Be kind whenever possible”
14th Dalai Lama
Name: Christopher
New Brunswick, NJ, USA (Zone 7a)
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AquaEyes
Mar 25, 2020 6:00 AM CST
First, you have to divide remedies into two groups -- systemic curatives, and contact preventatives. This article explains them:

https://www.rose.org/single-po...

For a good list of available fungicides used on roses, see below. You can then do individual searches for each to learn more, and decide if they are things you're comfortable using.

http://rosemania.com/page5.htm...

I've found that many products -- and their generic equivalents -- are available at either site below:

https://www.domyown.com/

https://doyourownpestcontrol.c...

If you're already seeing blackspot, you'll want to start with a systemic curative to kill the infection. After that, you'll use one of the contact preventatives to keep them from getting reinfected. There are several organic fungicides out there, but aside from those utilizing beneficial bacteria that kill the fungi -- such as those containing Bacillus subtilis, like Cease -- the rest are basically contact preventatives. This means that if your roses are already infected, using things like potassium bicarbonate, Neem oil, etc. will not fix the problem. You'd be better using them AFTER using a systemic curative to prevent new infection.

Some products containing Bacillus subtilis:

https://www.arbico-organics.co...

So if you want my recommendation at this point, I'd say to use a chemical systemic curative now, possibly repeating it a second or third time, seven to ten days apart (whatever the label says). Then switch to something as a preventative like potassium bicarbonate, perhaps with some kind of sticker-spreader that will prevent or reduce wash-off from rain. Avoid anything with oil (like Neem) when temperatures will be going above the low 80sF. This would also be a good time to try one of the beneficial bacteria products, since (supposedly -- I haven't tried them) they'll eventually colonize your garden and step in on their own to kill a future infection without regular reapplication.

Another spray product to consider is actually listed as a fertilizer, but seems to offer some preventative protection -- DynaGro Pro-TeKt. That might be something worth mixing with the potassium bicarbonate.

https://dyna-gro.com/product/p...

available here:

https://www.greenhousemegastor...

By the way, I found a cheap source for potassium bicarbonate:

https://labelpeelers.com/potas...


Personally, I prefer not using the "big guns" chemical stuff. But for the safer organic stuff to really work best, you need to begin with a fresh start. If you were just starting your garden and used them from the beginning, you'd have things more under control. But using limited amounts of the "big guns" at the start, you'll be better able to achieve a compromise between keeping things looking good and not having to don protective chemical gear regularly. Think of the "big guns" like antibiotics or strong medication -- if you're already sick, you'll need the intervention to get healthy. Then you can STAY healthy without the "big guns" by sticking to more "natural" methods.


:-)

~Christopher
[Last edited by AquaEyes - Mar 25, 2020 6:07 AM (+)]
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Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Mar 25, 2020 8:04 AM CST
Christopher, excellent information and websites! Could I say that concerning systemics, which I am not against using in general, if you are concerned for bees please do not use any containing neonicotinoids? when I checked my rose products, I found a combo systemic that contains one. Good too also about Neem oil, here we can't use it past early May, it burns the leaves of any plant it's used on. And this is using recommended amounts.
Amazing how right now my rose leaves are perfect. I hope I can keep them that way. I am considering using on of the ones containing the bacillus, I've seem info to recommend it for tomato diseases too, which I have in abundance. A gentleman at my local farmers market recommended Serenade.
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Name: Christopher
New Brunswick, NJ, USA (Zone 7a)
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AquaEyes
Mar 25, 2020 8:27 AM CST
The neonicotinoids are SYSTEMIC INSECTICIDES, not fungicides. That you found it in a "combo systemic" is not surprising, but it's not something you'd find if you were getting a fungicide separately. As with my thoughts on the "big guns" fungicides, I'm of the opinion that if you have a serious insect issue -- and I'm talking about something like rose midge, not something like aphids, which I consider minor -- then a judicious use of a neonicotinoid can still be relatively bee-safe. What I'd do is check first to see how long the neonic systemic will be active within the plant, then use it during a non-flowering period that will extend slightly beyond that time frame. So, for my region, that would mean starting at leaf-out in early Spring and extending to just before the first flush. That way, the only insects affected by the insecticide will be those eating non-flower parts of the rose, and you can knock out or down the pest population for the season.

If you garden where roses don't go dormant and need to attack a rose midge issue, you could always pick a time of year when flowering is diminished, anyway, and carefully spray just the roses. Then, commit yourself to removing EVERY flower bud that forms for the duration of the time that the roses will be systemically toxic. When you're satisfied that there is no longer any rose midge damage, cease use of the insecticide, wait for the duration period to pass (see the label for duration of effectiveness, then maybe add a little more time), and then let the roses resume flowering. The bees get poisoned if they eat the poisoned nectar or pollen, but there won't be any of that available to them on the roses if they aren't blooming. Also, be sure that the time of day when you spray is when the bees aren't active -- such as very early in the morning. And for rose midge, focus spraying on just the new growing shoots, which is where the adults will lay their eggs. Since the roses will keep growing, you'd have to repeat the spraying at the growing shoots weekly for about a month to really knock out the population for a season.

:-)

~Christopher
Name: Mike
Long Beach, Ca.
Charter ATP Member I was one of the first 300 contributors to the plant database! Roses Region: California Hummingbirder Farmer
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Calsurf73
Mar 25, 2020 8:54 AM CST
Excellent and well thought out advice. Hurray!
Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Mar 25, 2020 8:58 AM CST
Christopher, that is very true. A lot of people here just grab anything off the shelf and use it on their roses all year long. The combo formula I had was one containing a pesticide, which I don't really need. Twenty lashes with a wet noodle on me for not reading the label! I know better now.
All that you say excellent advice. I never spray anything. when bees are active, I like to err on the side of caution. Other than blackspot and tomato diseases, I'm really lucky that those are my only real garden issues. I don't have insect issues, except for aphids on occasion. I did have an infestation of aphids last year in mid summer, late in the year for here. I had three different colors, orange, green and brown. None of the aphids were on my roses. I used soapy water on them.
“ Be kind whenever possible”
14th Dalai Lama
Minnesota (Zone 3b)
RpR
Mar 25, 2020 11:32 AM CST
gardenfish said:Christopher, excellent information and websites! Could I say that concerning systemics, which I am not against using in general, if you are concerned for bees please do not use any containing neonicotinoids? when I checked my rose products, I found a combo systemic that contains one. Good too also about Neem oil, here we can't use it past early May, it burns the leaves of any plant it's used on. And this is using recommended amounts.
Amazing how right now my rose leaves are perfect. I hope I can keep them that way. I am considering using on of the ones containing the bacillus, I've seem info to recommend it for tomato diseases too, which I have in abundance. A gentleman at my local farmers market recommended Serenade.

I am impressed with the one site of Chris' for the list of products, especially as it lists name changes.
I have spent hours searching for such products, partly due to price and that has saved me a chuck of dough at times, but have never seen that one.
I use this on roses, tomatoes and squash, though one year I had it for use it on corn with rust.

I always by the 2 or 2.5 gallon size or some thing similar as it is cheaper in the long run.
I now have Serenade, Sonata, Oxidate and Actinovate for use in non standard rotation so bugs cannot adapt.



Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Mar 25, 2020 3:02 PM CST
I've been considering Actinovate, too. Margie on this site recommended it for roses. She warned me about the fact that it is dated. My question; if you are ordering actinovate online, how do you get a good date on it? It's not available locally.
“ Be kind whenever possible”
14th Dalai Lama
Minnesota (Zone 3b)
RpR
Mar 25, 2020 4:07 PM CST
All you can do is Email the source and ask.
It tech. , to cover their butts, is said to lose 10 percent per year after Exp. so unless you use very little, just increase dose.
I increase dose any way, so I do not worry.
Using rain or non-city water is a good idea.
Coastal Southern California (Zone 13a)
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jerijen
Mar 25, 2020 5:27 PM CST
Blackspot isn't a real issue here -- but we do get roses that rust, or mildew uncontrollably.

Rather than spraying, we just get rid of those roses, and plant something without that problem.

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