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Old 07-25-2012, 01:07 PM
Fine Gardens Landscaping Fine Gardens Landscaping is offline
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Roses- black spot/rust organic treatment

My customer has the common black spot and rusting leaves on some of her rose bushes. She likes to do organic options when possible. Her main concern is that she doesn't want to do anything that harms the bees that visit her garden.

I've been looking online and there seems to be lots of information and options for how to treat black spot and rose rust. Some say you have to do a series of preventative sprays nearly year round. Others say you can treat as needed.

Please, what has been your experience with this and can you recommend a good treatment option?
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Old 07-25-2012, 01:26 PM
rlitman rlitman is offline
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Black spot can really only be treated with preventative treatment.
Once the spot is on the leaf, the leaf is doomed. Best option at that point is to prune and spray, or else the spot puts off spores that infect the other leaves.

The official "organic" treatment involves bordeaux powder (copper based), which is probably more harmful than most of the real fungicides, and is less effective.
Fungicides should not be harmful to bees. They may be harmful to fish, but again, copper is probably the worst of these, and that's "organic".

Banner Maxx has worked best for me (but as with all fungicides, you shouldn't just use one because of resistance). I use Banner Maxx, Daconil, and Triforine, all together. I spray every 2 weeks if it's rainy. If it is hot and dry, I'll stretch that out to a month.
The Triforine (Rose Pride) can be sprayed weekly. The others can hurt the plant if sprayed too frequently.
I've heard good things about Mancozeb too.

The most important time to spray, is when the leaves are developing, and are soft and reddish. This is especially important if you have an active infection. Spray the preventative treatment on the new developing leaves, and your whole plant won't get defoliated.

Last edited by rlitman; 07-25-2012 at 01:30 PM.
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Old 07-25-2012, 09:14 PM
NattyLawn NattyLawn is offline
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You can try raw milk. It has to be raw milk, as in not pasteurized, with all the good guys in there to fight the black spot. 2 parts water to 1 part milk, sprayed weekly. The milk solution will leave a white film, but that should wash off when the plant is irrigated or watered.
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Old 07-25-2012, 10:59 PM
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Landscape Poet Landscape Poet is offline
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Copper Hydroxide - found in many fungicides but look for trade name Cupro. Simple cheap and last time I checked Copper was Organic but I am not sure if the complete package would be considered organic. Either way it should handle your black spot and not harm the bees if used according to label.
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Old 07-26-2012, 11:39 AM
Fine Gardens Landscaping Fine Gardens Landscaping is offline
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Thanks for those explanations and suggestions guys. I feel like I got a better understanding on what some good options are now.
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Old 08-02-2012, 06:08 PM
Smallaxe Smallaxe is online now
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I had black spot real bad on a particular rose for years... then I moved it out into full sun and plenty of open air, which solved the problem completely...
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Old 08-03-2012, 12:36 PM
rlitman rlitman is offline
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Quote:
Originally Posted by Smallaxe View Post
I had black spot real bad on a particular rose for years... then I moved it out into full sun and plenty of open air, which solved the problem completely...
It can help. It depends on the climate and the rose though.

They say to prune it to get more airflow between the leaves, to prune back any growth near the ground (where splashed rain water can bounce up onto the leaves), and to use mulch to prevent splashing.
Oh, and don't water from above.

I've done all those things, and still, I have been battling the issue for years. I have noticed that the roses with the shinier tops of leaves, tend to be a little less prone to black spot. I guess that the thicker cuticle helps rain water roll off.
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Old 08-03-2012, 07:25 PM
Dr.NewEarth Dr.NewEarth is offline
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A table spoon of baking soda in a quart of water sprayed on the leaves will help.
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Old 08-18-2012, 08:58 AM
Smallaxe Smallaxe is online now
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Originally Posted by Dr.NewEarth View Post
A table spoon of baking soda in a quart of water sprayed on the leaves will help.
Interesting that you say that... I use a baking soda paste for canker on apricot trees...
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