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Black spots, yellow leaves on roses


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daisybeans

annapolis md
Posts: 3675
Posted: Tue Apr 28, 2009 11:19 pm   Post subject: Black spots, yellow leaves on roses


Hello Rose people,
This is what I see happening on two of my rosebushes... If I recall correctly, it has happened in other years. Is it something I have to do something about? Thank you!
Daisybeans.



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Sjoerd

West - Friesland
Posts: 9407
Posted: Tue Apr 28, 2009 11:49 pm   


I think that it caused by Diplocarpon rosae. It is commonly known as "Rose Black Spot", I believe. It is a fungus.

The treatment possibilities are a bit bleak, I'm afraid...but here are some things you can do:
(1)Fungcidal spray or powder. It won't cure the plant, but it will help to contain the infection. You will need to re-apply the anti-fungal every 1-2 weeks and after heavy rains.
An example of a spray is: chlorothalonil, and an example of a powder is Sulphur. There are several choices. I would advise you to go to a garden center near you and see what they sell...then ask an employee that seems to be someone that understands botany rather someone who is just working there for a paycheck and does not demonstrate knowledge or interest. The owner or manager might be a good place to start.

(2)Try and keep leaves dry--this means a sensable pruning that allows good air flow, having the rose bush located in the sunniest of places. Never give the rose plant water by spraying it with the garden hose--give water directly the soil at the base of the plant.

(3)Remove affected leaves as soon as you see them. It is best to burn them. Clean up all dead leaves that have fallen onto the ground under your rose bush.Do this during the summer, but also in the winter and spring. In the spring you can then add a thick mulch after feeding them. This way the spores can not be splashed up onto when it rains.
You can also remove the branches (canes) in the fall that bore infected leaves.

(4) If all else fails you could try moving your plant to another location and continue your protective measures.

I may be wrong about this, but I have the feeling that if your rose gets this fungus it is going to keep it forever, as the fungus not only exists on the ground at the base of the plant, but also can reside systemically in the branches of the rose.
In my experience, it is just a continuing battle of containment--and Holland is moist, so the prognosis here is poor. Confused Hopefully there it may be warmer and dryer, and then there is good reason for optimism.

Good luck with your precious little plant. Keep us posted how you get on with it, ok?



Last edited by Sjoerd on Tue Sep 23, 2014 10:08 pm; edited 2 times in total
Patches
Great Content x 1
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gardengater

NC
Posts: 1544
Posted: Tue Apr 28, 2009 11:54 pm   


Sorry to hear about your fungus. We battle it always here in the south. All that Sjoerd says is true. I've had bushes recover with regular spraying of fungicide and clean up.

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Netty


Regular Plants Contributor

Southern Ontario zone 5a
Posts: 13326
Posted: Wed Apr 29, 2009 12:15 am   


I recently heard that milk sprayed on Black Spot helps. Has anyone tried milk?

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dooley

Texas
Posts: 6536
Posted: Wed Apr 29, 2009 1:02 am   


I've had that and the bushes here have it. Just pick off all of the affected leaves and trash them. Don't let them fall on the ground. Put milk into a spray bottle and spray the bushes being sure to get the bottom and the top of the unaffected leaves. You can spray again if you need too but it's always worked for me. I've been picking the leaves off of the bushes here but haven't finished it. Now, it's raining so it will probably be worse when I get to it again. The bushes are doing so well otherwise. dooley

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daisybeans

annapolis md
Posts: 3675
Posted: Wed Apr 29, 2009 1:10 am   


Oh dear... well, that sounds daunting, but ... at least now I know what to do !!! I'm going to print this out and study up.

You guys are awesome. Thank you so much. I'll keep you posted. Hopefully all will be well.

Sjoerd, I know what you mean about the various types of garden center people. I think I know just who to go to for good answers. FYI, it is hot and very humid here in Summer.

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glendann

Texas
Posts: 9512
Posted: Wed Apr 29, 2009 1:33 am   


I have tried fungal spray and it never fazed it.I take all the spotted leaves off and burn them and I spray really well with milk as dooley said .It works.

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daisybeans

annapolis md
Posts: 3675
Posted: Wed Apr 29, 2009 1:41 am   


OK, this may be a dumb question... but does it matter if it is regular milk or will fat-free work just as well?

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glendann

Texas
Posts: 9512
Posted: Wed Apr 29, 2009 1:48 am   


I use regular homo milk and 2% on mine.

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daisybeans

annapolis md
Posts: 3675
Posted: Wed Apr 29, 2009 1:57 am   


OK. I'll try that as soon as we get through the rain predicted next 4-5 days.

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glendann

Texas
Posts: 9512
Posted: Wed Apr 29, 2009 1:59 am   


Its the only thing that has ever worked .I pulled every leaf of my big pink rose last year and it has bloomed this year.

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Sjoerd

West - Friesland
Posts: 9407
Posted: Thu Apr 30, 2009 12:05 am   


Let me know how the milk treatment works, Daisy. I would be very interested.
I have used milk mixed with rainwater to treat mildew on courgette and cucumber leaves--but never on roses.
Thanks

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daisybeans

annapolis md
Posts: 3675
Posted: Thu Apr 30, 2009 12:39 am   


I will surely let you all know what happens. I picked up some "fat" milk today but now it's raining. I picked off a lot of leaves... Thought I would spray the milk when the rain stops... I wonder how long before I will be able to see if it is helping. Thought I would also go to the "good" nursery on the weekend to feel out the folks there.

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daisybeans

annapolis md
Posts: 3675
Posted: Wed May 13, 2009 3:46 pm   


Update on my roses suffering with black spot fungus... I have been picking off the diseased leaves and spraying with milk. Two of the three look much better -- the young climber on the fence and the old American Beauty. The oldest and largest has the most widespread problem and I will really have to be diligent with it. Last night I picked off a full grocery bag of leaves and cut off a few of the most diseased shoots. Sprayed again. It is against a wood fence so I am wondering if that also holds the fungus (I'm sure it restricts airflow). All have buds (yay) and the American Beauty has several so that is good as in the past couple of years it has only gotten one. I found this site with holistic remedies for what ails the garden. I am going to sprinkle some cornmeal around the roses -- has anyone ever heard of this?

http://www.gardengal.net/page11.html

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