Black spots on roses

[dina]

Hi,
one of my rose bushes has black spots on ALL its leaves. I know that it is a fungal infection but I don't want to use chemicals. It would be difficult to cut all its leaves so I wonder if I could simply prune it now in the beginning of May?
What else can I do to fight this fungal infection? Some advise,please.
Dina

[Kisal]

I found this, but I don't know how well it works:

http://www.rose-growing-tips.com/Main-M ... dening.php

"With organic rose gardening it is even possible to make organic fungicides. For example, a 50/50 solution of milk and water will control powdery mildew. Another popular antifungal treatment is a mix known as the Cornell Formula. Every organic gardener has their own recipe, but they are all variations of mixing one tablespoon of baking soda and one tablespoon of horticultural oil with one gallon of water, which should be sprayed onto your rose plants every seven to ten days."

[cynthia_h]

Kisal's source is good, and I had *some* success last year with neem.

The neem seemed to keep the black spot (yes, that's the name of the problem--black spot) from spreading to other roses, but we were careful to spray at the end of the day, so as to avoid killing pollinators, active during daylight hours.

The neem was recommended for use every other week at the stated concentration. Unfortunately, we were only able to do the "every other week" routine for about eight or ten weeks...

Winter control for black spot is to rake up ALL dropped foliage and use dormant-spray oil. Well, we raked up all the foliage but didn't get to the "oil" part this winter. But the roses are blooming quite well anyway, despite their black spot and (I just saw on Friday ) powdery mildew...

Gotta get the neem out again.

Cynthia H.
Sunset Zone 17, USDA Zone 9

[dina]

Thank you for your replies. I've found that link useful.
Dina

[Sharon Marie]

unfortuneately I have noticed some black spot on mine too. I have tried neem oil with no success. All of my roses are more than 2-4 feet apart. Will the black spot spread even though they are that far apart. I'm a newbie rose gardener. I did prune some damaged leaves that these little white catterpillar looking things did in just one day. I look at them daily. In one day these little white thingies took over an entire 2 bushes!!! I went straight to the store and got some incecticide with neem oil. Two days later, they were back. I coated the whole bush inside and out. So, I bought some chemicals (ewweee) and that has worked well. What should I do about the black spot though? Will it spread??

[Kisal]

Black spot of roses is a fungal disease. It spreads by airborne spores. If that's what your roses have, then yes, it can spread from plant to plant.

I'm sorry, but I have no idea what the white caterpillars might be. Can you post a picture of them?

I suppose you might have both a fungal infection and an insect infestation. I would think the neem oil would have killed the insects, though.

[Sharon Marie]

I do not have a picture of the little catipillar thingies, but they were less than 1/2" long and looked like white catipillars. The black spots I'm pretty sure is the black spot disease. Will my rose bush definitely die if it gets it?

[cynthia_h]

Black spot doesn't kill established roses, nor do rust or powdery mildew.

They just make the roses look yucky (that's a technical term... ). I've been struggling with these roses ever since we moved to this house in 1997. (Not as consistently every year, some years I could hardly move, and the roses were on their own....)

I dug out one of my roses a couple of years ago, thinking that the improved air circulation (they're pretty tightly spaced, given our small planting area) would bolster the remaining rosebushes' ability to fight off these disorders.

No such luck, but at least one rose which had previously not flowered at all was scared into production!

Cynthia

[Sharon Marie]

Well, I checked the roses again today. They seem to be doing better. It's been 8 days since the last application of the disease / insect control. I applied a second dose today. I also covered some of teh other plants in the garden too. It looked like bugs have been eating hols in my black eyed susans. Why the sudden mass of bugs this year?? We moved here last July.. .and the garden areas were SO healthy!!! I need to elarn about prevention (like an ounce of prevention is worth a pound of cure). Any advise?

[Sharon Marie]

[Wahrheit]

Hi,
one of my rose bushes has black spots on ALL its leaves. I know that it is a fungal infection but I don't want to use chemicals. It would be difficult to cut all its leaves so I wonder if I could simply prune it now in the beginning of May?
What else can I do to fight this fungal infection? Some advise,please.
Dina

Not having the benefit of seeing a picture, my guess would be either downy mildew or black spot disease. Many people often confuse Black spot with Downy Mildew.
See picture and description of Downy Mildew here:

http://plant-disease.ippc.orst.edu/dise ... cordID=985

With Black Spot, some cultivars are far more prone to it than others.
prolonged humidity and dampness can aggravate it, luckily both diseases can be controlled without harsh chemicals. I use a product called Soap Shield with EXCELLENT results.

It is available through www.gardensalive.com.

I also tend to avoid cultivars that are
persistently problematic (especially with Black Spot)
Hybrid Teas are beautiful, but most (although not all) are a problem.
Most of the Rugosa roses are Black Spot free. Also Lady Elsie Mae, all the Knock Out roses, and MANY others.

Preventative maintenance is your best option, as Black Spot is much easier to prevent than control once it is present.

Good Luck!

[fhhs]

i think i have more than one problem here...some leaves got yellow(lack of nitrogen?) and they have black spots while some leaves also have white insects that are so tiny(right now) idk how worse its gonna get. help me out plzzz
pics:

http://img35.imageshack.us/img35/8138/img0007oum.jpg
http://img37.imageshack.us/img37/5851/img0008xai.jpg

[Kisal]

The pics are too small for me to see anything. My guess is that the white insects are either aphids or mealy bugs. If they move around, they're aphids. If they look like little stationary gobs of cotton, they're mealy bugs. You can control aphid by spraying with an insecticidal soap solution or neem oil. You can also kill mealy bugs by dipping a cotton-tipped swab in rubbing alcohol and gently touching it to each of the bugs. It's rather labor intensive, but it works. I use that method on my African violets.

The black spots are probably black spot of roses.

Sorry I can't tell you anything more definite. Could you post close ups of some of the damaged leaves, or of the bugs themselves?

[Wahrheit]

i think i have more than one problem here...some leaves got yellow(lack of nitrogen?) and they have black spots while some leaves also have white insects that are so tiny(right now) idk how worse its gonna get. help me out plzzz
pics:

http://img35.imageshack.us/img35/8138/img0007oum.jpg
http://img37.imageshack.us/img37/5851/img0008xai.jpg

If it were my roses, I would apply a regular weekly spray routine of a product called SoapShield for what appears to be a fungus problem. In extreme cases it wouldn't hurt to spray them twice a week for the first couple weeks.

I also use a pyrethin based insecticide called Pyola. it is a contact spray for your insect problem. It can be helpful when necessary, as it will only kill the insects that are sprayed.
I would advise against systemic insecticides and harsh chemicals, because they will kill off the good insects such as Lady Beetles.

[fhhs]

thx for your responses. sure if the pics are too small, heres a link for the album with my infected leaves' pics. any suggestions or advise will be appreciated.thank you

link:
http://img20.imageshack.us/gal.php?g=img0006c.jpg

i have some other leaves with same problems too in this album so just to clarify: all of those pics arent of the rose bush.

[Kisal]

Well, the white bugs definitely look like aphids to me. You can wash them off with a stream of water from your garden hose. You will have repeat the washing whenever you see more aphids on the plants.

The aphids suck the sap from the plant, so the yellowing leaves could be caused by them.

Information on control of Black Spot is given at the beginning of this thread.

[cynthia_h]

I would say you're dealing with leaf hoppers and aphids. Take a look at www.organicrosecare.org for some assistance in dealing with these pests.

Also take a look through both sections of our Rose Forum for past threads with more info in them; there have been many rose-savvy gardeners here who aren't posting currently and whose advice is excellent.

Cynthia