I don't think I've ever seen blackspot on canes, and your images aren't close enough for me to tell what you are referring to. I do see a couple discolorations that might be some canker (kind of dark reddish-purplish). I usually try to cut below all canker, but sometimes that could also be "sun-burn."

I'll be curious to see what other posters have of offer on this.

My two Double Knock Outs never get BS. If yours get it this coming year, why don't you post some close-up photos so we can see it. It's possible that it is a different kind of fungal disease instead.

You do have your rose in at least 4-6 hours of sun, don't you?

Kate

I agree with Kate on the canes. There is no need to remove the bushes if you would like fresh canes you can always prune to the crown and fresh canes will grow. I've never had black spot on mine either. I have had spot anthracnose on them thou.

There are spots like this on pretty much every cane :( so just take the ones off with the worst of it? On some plants that will only leave 1-2 canes unfortunately. Is that safe for the plant?

My row of 12 pink double knock outs are all 4-6 feet tall now, are starting to break bud and practically all their canes look like that. They also looked like that last year in the late winter/early spring. I did nothing. The plants all grew and did well. I really don't think it is a fungus infection. Or if it is, then it is small enough that the plant's own natural defenses can kill it.

Yes, black spot can winter over on the canes. We experience this a lot in colder climates. You can take it off if you choose, and now would be the best time to do that, or you can leave it and spray them instead. Either way it won't prevent you from getting more black spot this season. Regardless of what you do the spores are out there, in the air and soil and other plants, and when the conditions are right they will show up again. It isn't something you can do away with permanently. You have choices. Either experiment with a lot of roses until you find some that are resistant in you garden, spray on a regular schedule or learn to live with some spots.

As I said, this is the time to prune hard. It's very early spring and the plants are in full growth mode. If you cut them way back now they should rebound with good new growth for you. KOs are very vigorous growers. I think they'll be fine if you prune them hard.

It might be Downey Mildew. Knock Out's will get this disease.

I can certainly see the spots now. Could also be anthracnose or downey mildew, If it were my rose I'd remove all of the canes. The rose will grow back and won't have those canes to reinfect it again.

I like what Seil said about regardless what you do the spores are there in the air and in the soil and when conditions are right they will show up. My knockout gets that purple red every year over winter. I never see black spot on the leaves. I have grown a dbl knockout and 24 pink knockouts and they never gets black spot on the leaves.

Compost has more disease resistance than wood mulch according to the Ohio State University mulch study.

Cornell University says 3" or 4" can be over-mulching with wood chips and can suffocate the roots and cause cankers to develop around the base A better practice is to renew the wood mulch every 2 to 3 years and churn up the existing mulch or rake it before adding a light renewal layer.

It's better to keep the wood mulch 6" to 12" away from the base according to the Iowa State and Kentucky Universities.

Texas A&M recommends compost as mulch.

Exactly what roses do you have?

The bright red original Knockout roses are usually quite resistant to BS, while most
David Austins are quite susceptible to BS. One might guess that it isn't BS, but one can't rule it out entirely based on the information I have available.

This blog page may help.
Rosmania blog on BS vs Downy

The advice at the local rose club was that a soil drench works best for Downy as it gets into the entire plant--not just the leaves.

Are we even sure it is BS? As I said, this happens on my double KOs each year and they do quite well with me not doing anything at all.

Jessica you may be tired of hearing so many different opinions by now. But all of these diseases are much easier to diagnose in the leaves. Each one of these has a characteristic look thats much easier to see when it's on the leaves. I can say that it's not canker and most likely not black spot given the cultivar. I did have anthracnose last season but it only spread to the canes on one rose.

If this should happen next year take a photo of the leaves. Get a picture of the front and back of leaves and it should be easy to help you.

Due to the defined nature of those spots I'm rather sure it's not downey either. But I'm not an expert. That leaves anthracnose or cercospora and they can over winter on the canes. I would remove the canes and start fresh.

Some canes on our Double knockouts look like that... But I see no BS on leaves during growing season and the ones here still bloom well even with those spots so I do not worry about it here...

As Jim and I noted, our double knock outs do fine with canes that look like that. I would not remove the canes.

Thats good to hear Jim and Braverichard. Mine after a winter like this one are not cane hardy anyway. If I ever get another slightly milder winter I shall try leaving them on. Thanks

Your last picture looks very similar to the die-back I've been experiencing this fall and winter. I could be blackspot or it could be some other kind of fungal infection or bacteria.

Has it been exceptionally wet in the area with more cloudy days than not?

-Adrian.

Thank you so much everyone for your advice and input! The spots aren't new I don't think; they are carry-overs from the summer back when we had something causing yellowing/spots on all of our leaves that caused defoliation of the plants. From looking at the pictures of the diseases y'all have mentioned I think it's either black spot or downy mildew, but am still not sure which. I will definitely take pictures if/when it happens again this year, but was hoping to KEEP it from happening again, hence me asking what on earth I can do now with these canes- a preventative spray, cutting them all off, etc. it breaks my heart a little to think of cutting them back to the ground, but I can if that's the group consensus. Or if I can just start spraying now with a fungicidal spray to keep something major from coming back.., I don't know. It was very sad last year to see how terrible they all started to look, and I didn't expect that from KO's!!

I did not offer advice on preventing those spots because I am no spray here Jessica...

When you say your Ko's looked terrible last year do you mean the canes? OR leaves too? etc?

Mostly the leaves- spots, yellowing, falling off, and fewer flowers then on the plants. I didn't notice the canes had gotten bad until later on!

Without pics nobody really can be sure so this is a guess... Ko's do get blackspot etc. in some areas. Your area just might be one of them Jessica Skelley..

Here the spots on our Double KO's canes has not effected there performance or blackspot resistance. So not sure what to tell you about your spotted canes...

Here are some pics of some of the new leaves coming in...

Not good that they are growing back already diseased. It does resemble downey mildew. I swear no matter wear you are in the states KO just does not get black spot this fast. I'd be quite worried about DM. Even thou infection aren't common. It can happen.

Patty is there any way to treat it/prevent further spread other than cutting back the entire bush to the ground?

I wish I knew what to say. Also wish there was a downey mildew expert on here. From all that I read dm is most common to Florida and the coast of California. I don't worry about cutting canes all the way to the ground because these roses grow back with nice healthy new canes. If it is dm it will spread to your other roses. Ken was the first to chime in with dm and he is a good rose grower. Since the infection is already spreading again IMO I'd get the canes out immediately no matter what it is. But thats how I feel. There are recommended sprays. But why chance it when you can cut back the canes remove the debris and quite possibly never see it again. Hope someone else has something to say. I hate being the only one. I've only seen dm once on one bush in 20 years. It was cut to the ground within the hour. That was scary looking and spread like crazy on the bush. I'll be wishing you luck with what ever you decide.

study on fungicides for Downy Mildew

It says that Alliette did a fine job as did Stature DM. Some control was obtained with Mancozeb but this fungicide may have health risks. This study supports the idea of using a soil drench to control Downy Mildew--especially in this case where the canes are infected.

I trust Seil. Seil has won awards for her roses.

Fungus is always there in the air and in the soil.

I would try another mulch rake the mulch and spread finished compost to change the soil to the good fungus to get rid of some of the disease fungus.

Successful Garden Mulching for Dummies

http://flip.it/xkrRQ

Thank you Zack I could not think of the names of those chemicals.

Jessica is there Ag department or rose society near you by any chance. That way you would be able to have the disease properly diagnosed. I also don't mean to sound to dramatic about your roses. If this were not KO I'm not sure what I would think. But for a KO to have sick leaves as soon as she leafs out isn't normal.

I agree with Patty I would have someone in your area familiar with fungus diseases diagnose your problem to be sure... If that's possible...

Alliette is rather expensive. Mancozeb and Daconil will do the job. Mancozeb is rated caution, the lowest toxicity designation while Daconil is rated warning, which is higher.

This study and the other one I posted says that Daconil is ineffective.
http://www.rose.org/wp-content/uploads/2011/03/Downy-Mildew.pdf

This study says that temperatures over 80 degrees for 24 hours will kill the active spores. It isn't usually an issue if the temperatures heat up quickly.
But, it can kill plants if the temperature and humidity are optimum for its needs.

I agree with Seil. Every year I see this on a few of my roses and I assume it is blackspot. I do live in colder climates as well. There is nothing you can do except prune the badly affected canes (if you want to go organic) but this is an indication that this plant is prone to bs in your area.

Hi there - I'm on Cape Cod in Massachusetts and wrestling with the same issue as Jessica Skalley. I had a very bad case of black spot 1 or 2 years ago and even at first foliage this year the leaves are still infected. The canes too. I am thinking of just pulling the six plants and getting new ones next year (I am not patient enough to cut down and have the canes grow back, plus I suspect they will just grow back infected). I tried using BioAdvanced All in One rose fertilizer before just as a saw new growth (mid-March) this year, but I think that did more harm than good. I think I stressed the plants out. So... now its just a big mess! (Not to mention that I didn't prune at all the first two years because I didn't know you had to prune KO roses so aggressively, so they are rather leggy which I don't like.) I am thinking most here would be on board with me trying from square one. That's the way I'm leaning - I'm not sure these plants can be recovered. When I start again next year, any advice re: pruning/feeding when starting out plants on Cape Cod? My thought is just to get a better start on pruning after they are first planted, and then to use an organic leaf spray rather than a strong fertilizer as I've done in the past. (I think the BioAdvanced is just too strong for me as a beginner gardener to work with.) If any one has any advice, it would be most welcome! (I thought knockouts were dummy proof - but I guess no one had me in mind, lol!)