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Confused about Black Spot or Brown Spot on Roses

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by Southern Gardener on May 06, 2006 09:14 AM
I am very new to growing roses so please forgive my ignorance.

I have a rose bush I planted last summer, it is an old variety named "Christopher Marlowe."

I have been reading many of the posts in the forum concerning Black Spot and I'm not really sure if this is my rose's problem... As soon as the new growth began this spring many of the leaves emerged with spots- I think they are brown spots. Is this just a stage of "Black Spot?" The spots don't appear to be any kind of mold- they don't rub off.

Also many of the new leaves are a pale yellow- with the spots.

The bush seems healthy- loaded with buds.

I went out and picked off as many of the spotted leaves as I could find and threw them away.

My worry is that I will treat it for a fungus and that's not its problem. So before I treat it in any way I wanted some advice on what I should try.

We live in the central part of Virginia- and humidity is already a problem here so I kind of lean towards the fungus (fungi), but then the yellow leaves make me think low iron(?)- or maybe both are a problem! [dunno]

Thanks in advance for any advice!

by RugbyHukr on May 06, 2006 10:20 AM
you probably have a variety of mineral deficiencies, low zinc & copper can contribute to your conditions.

fertilize w/ rose food each year before growth

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I love the sweet scents wafting in the breeze. I stop to admire the vibrant colors of all living things. And people think me odd. Then ODD I am!!!
by joclyn on May 06, 2006 10:29 AM
yes, fertilize with a good brand each year.

sounds like you DO have black spot (your description matches what my rose looked like last year - and that was definitely black spot).

Ortho has a terrific product for this!! i'd tried a different brand the previous year and was not too pleased with it.

go for the Ortho Black Spot Treatment...easy aerosol spray - and i think the Ortho stuff actually got rid of it, too!! i don't see any spots this year (so far anyway)
by The Plant Doc on May 06, 2006 02:53 PM
I agree that it sounds like black spot, a good healthy plant is the best defense against diseases, but a lot of the time that is just not enough. Due to weather conditions the fungal diseases get going anyway.
I think the Ortho products are great, they are easy to use, and the directions are usually in lay mans terms. A few other things you may want to keep in mind would be, clean off any pruning tools with alcohol prior to pruning. Try to improve air flow around the plants if possible. Avoid if possible getting the leaves wet during bright sunlight hours. And resist the temptation to over fertilize. A lot of diseases can be pushed out with proper fertilization, but too much or too little can result more disease problems.

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Mike Maier
The Plant Doc
by peppereater on May 07, 2006 11:58 AM
There's a lot of evidence that too much chemical fertilizer can make a plant more prone to disease. Nitrogen in particular can cause excessive green growth, which isn't desireable. Some people report great results from Miracle Grow and other quick release fertilizers, and some people report many fewer problems with organic or other slow release fertilizers. I use Plant-Tone for most fertilizer applications, because it has a very broad range of nutrients, macro and micro, and is slow release. Roses have specific needs. I don't know if there is a Rose Tone or not, but I'm thinking Holly-Tone would be be a good, complete rose food...let's see if someone weighs in on this...

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Even my growlights are getting restless!
by The Plant Doc on May 08, 2006 12:56 AM
Holly Tone used to make a special product for roses in particular called, "Rose Tone". I used to use it all the time and found it to be a very good fert. It is a mixture of fast and slow release N with the normal macro and micro nutrients.

As far as the fert causing the lush green growth being bad for the plants, I really don't think that is it. Take lawns for example; Some diseases such as dollar spot, and anthracnose grow in a high nitrogen environment. While some diseases like rust or leaf spot can be pushed out with a good application of fert. But some slow release ferts like milorganite while not being readily available to the lawn itself, still create as soon as its applied, a high N environment for the diseases to take off in. That is why most of the commercial lawn care companies that offer "the organic solution" have a lot of problems with disease control on their lawns. The plants do not have the immediate benefit of the fertilizer but the diseases do, so they can do their damage while the plant is weak, and not actively growing yet. The fertilizer at ground level while not having a direct impact on the leaves of a rose do create the right settings for the disease to be vectored in through roots or by insects.
I think a big reason why Miracle Grow has pushed a lot of diseases in roses is that people tend to water right over the top of the plant instead of at watering at the base. This creates N deposits on the leaves, which can not only make it suitable for diseases, it can also burn the leaf tissue.

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Mike Maier
The Plant Doc
by twwright on May 22, 2006 12:17 AM
Wow! Great advice! I too have problems with Black Spot on Roses and am guilty of the Miracle Gro watering of the leaves thing. I just know I have spread black spot to another rose bush by watering or fertilizing the leaves (foliar feeding) instead of feeding and watering at the base. Just don't want to bend down that far. Laziness never did get me anything but trouble. Also, I've learned to watch out when I buy a bush from the nursery because they often are so good about pre-loading the rose bushes with black spot for you! How nice of them...
Also, don't put these pulled off leaves with black spot in the compost pile for gosh sakes, burn them if you can. Somehow they always seem to creep out of the garbage can and crawl back to another plant to spread their disease. I haven't found a product that works well so I'm eager to find this Ortho product. I wish you would just tell me what it is. "That" Ortho product doesn't tell me much. "Which" Ortho product is it? There are jillions of Ortho products. I already get confused just walking up to the wall of chemicals and catch a whiff of the smells. Get dizzy ya know. Anyway, you guys have great advice here and I appreciate the service.
by joclyn on May 22, 2006 08:52 AM
it's called ortho orthenex - garden insect and disease control.

provides system protection from insects diseases and mites.

it worked much better than the safer fungicide i'd used the previous year!!

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