What causes canes to turn black and die back?

I searched on some old threads and found it is caused by a fungus and is best prevented by spraying with a sulphur spray in spring before new growth.

In my case, I think several of the bareroot roses I bought in Feb. had a variety of dieback with cane canker. After blooming and being weakened by powdery mildew and blackspot, canker is finishing the job, although canker alone may have done so anyway eventually.

I also learned by reading an old thread, that you should disinfect the pruning shears after cutting back die back with black canes so as not to spread the fungus. That I didn't know. A bleach solution was suggested. I'm guessing that 70% rubbing alcohol would work just as good?

In the present case, this time it's Blue Moon that's succumbing. Even the bud union is black, but Dr. Huey looks like it's alive, peeking up through the soil.

This is a lesson to me that if I buy bareroot again, to avoid any with black spotches on the canes, or any with obvious die back that looks like canker.

Cold weather can cause it too.

So sorry to hear this Rosemary. If you can cut back the cane to where there is new growth or "clean" growth just above an eye, (at an angle) that will help. Also, not overhead watering will also help. We have had such a cool and rainy spring. It was perfect conditions for it.

If you post some close-up photos of what you think may be the canker, we can give you our opinions. Canes routinely die back for any number of reasons, just like many stems on perennials do (but we don't notice those as much due to their smaller size and greater number of stems). It can be a natural part of the plant going through its various stages.

Here are some pics:

Now that I think about it, the other two bareroot roses I lost were also lavenders, and I believe the cause was canker, only at the time I didn't connect it to a fungus disease, and I never sterilized my pruning shears. Maybe lavender roses are more susceptible?

Just did a thorough look at all my potted barefoot roses and several show die-back canes, some looking suspiciously of canker. Here is the next worse one, Oldtimer. Looks like a major cane is dying off and it could be canker all the way to the bud union like Blue Moon. It had some beautiful blooms I deadheaded a few weeks ago. I have kept them well-watered and maybe that has contributed to the problem:

Personally, I would throw them in the garbage. Maybe others can give you better advice...but if they were in my yard...they'd be gone.

Thank you for your opinion, Carol. This year is the first in about 25 years that I've bought any bareroot roses. I've never had to deal with canker on my established roses, so I didn't even know what I was looking at....until now. If I ever buy bareroot again, I will be looking at them a bit differently...definitely avoid those with serious fungal die back.

So true...I see people at greenhouses just putting roses in their carts willy nilly. They don't look at the length of the shank, for black cane or anything. Just plonk.

I pulled Blue Moon out of its pot and there were all healthy roots. I'm sure Dr. Huey would have done well. So far this year with new bareroot plants, I have lost Blue Moon, Angel Face, Orchid Masterpiece, and Secret (only one I planted in ground last Feb.), and I think Oldtimer will be the next one to succumb. I pruned all other dieback and most suspected canker. It's hard to tell sometimes when it looks mostly healthy except for a black spotch somewhere. I disinfected with 70% rubbing alcohol after each cut. Some plants are down to one cane.. My bargain roses are turning out to be not such a bargain! My two potted roses from Home Depot look good except for blackspot. The potted one from Green Acres looks the best (all three were planted in 10 gal. pots for now). And healthiest of all is the one from Regan Nursery (bareroot into 15 gal. pot), and Rogue Valley (band now in gallon pot.

My healthiest, fastest growing bare roots are from Regan also, I paid more but it was well worth it. St Swithun is branching out with a first bud getting plump. So anxious to see it bloom.
The healthy little band newcomers from Hummingbird nursery are doing valiantly, they have been a real joy to watch develop.
I am curious to know if some roses themselves are resistant to canker, or if it is time and chance that in the same bed in close proximity, some have terrible aggressive canker and some don't. The battle rages on with a few of my favorite Austins now down to one cane. It's distressing to cut off canes with buds forming, having never seen what the new roses look like.
Emma Hamilton and Evelyn are doing fantastic with a large batch of buds ready to burst, but William Shakespeare 2000 and Charles Rennie Mackintosh are suffering along, I may lose them.
Once again I am mad at myself for not getting a good rich dirt prepared before the roses came.
The good outweighs the bad, Madame hardy had the biggest fluffy blooms she has had in 6 years .

Of all diseases canker is foremost the most ellusive.... . It may become widespread for short periods and it takes its toll, but in most of cases it goes by slightly unnoticed until one sees it on a bush that was quite healthy and then going downhill...steeply. Partly because it is a stem disease and partly because it may have different causes: Bacterial or fungal. Does it matter? well as things stand out now not much. It is the plant equivalent of gangrene and parts have to go...mutilation... It may be the outcome of a very poor winter condition. Are the bacteria or fungi simply opportunistic taking advantage of a weakened bush? Or they are aggresive opportunistic using a scar produced by pruning getting into the plant tissues. They may be both... Imho, this simply shows the state of the art when it focuses down to plant immunity to diseases. I can venture that it is just not understood. We've come a long way since Pasteur times with animals ( us humans included), but the plant world is different and plant therapeutics is still a toddler in arms. Most available chems are directly toxic to us,pets or the environment; so prevention seems the only strategy . So giving plants a lot of early care trying to build up vigor for the first 5 (?) years seems sensible. I've seen canker on both bareroot roses ( less) and grafted ( mine all on R.multiflora). Have I've been able to overcome it? Yes in some cases when I decided to lift and pot my declining bushes making sure that they get as much detailed care as possible in my conditions. Last season I lifted all in all 27 bushes that needed extra care. All had had some degree of canker in the previous growing seasons. Of these I finally lost 3, 8 are still recovering ( second year of inside TLC) and 14 have regained vigor and belong to the group that will be placed in ground during these coming weeks. This season I detected about 11 that are/will be lifted. Of these two are own root climbers already inside ( Mme Plantier and Cl.Souvenir de la Malmaison) , the rest are grafted: one is a species rose R.roxburghii plena, one a climber tea (Safrano) , four are D.Austins (Gertrude Jekyll, Charlotte, Graham Thomas, Swan) the rest HT's and Flbs: Whisky Mac, Louisa Stone, Matterhorn. I guess this description just is a proof of how much I was able to improve my rose growing this past season since I reduced to less than a half those that visibly need extra care... My purpose in sharing this here at the RF is that in my view there seems little direct remedy but alternatively good management practises seems to reduce the risk of this ever present threat. For the time being, it would seem that one has to accept a certain toll on newly settling bushes. The choice of sturdy vigorous initial bushes is a definiteve first step. As it happens frequently bargains don't necessarily end up being so...
Arturo

Thank you for sharing your experience managing this problem, Arturo. I could have unknowingly infected some plants by not disinfecting my pruning shears early on when removing die-back caused by the canker. So at least I am wiser in that way, as well as not choosing suspect bareroots in the first place.

I am not sure I know what canker is. Can someone post pictures that compare "ordinary" die back and canker? I would greatly appreciate it.

Think I better get a fungicide fast. Any idea of one that works the best ?
It wasn't so scary when the affected part was near the top and I could cut it off, but I see Evelyn has a big dark spot near the bottom. I'm trying not to feel too discouraged , it's another storm of life.

Porkpal, ordinary dieback is deadwood brown. Canker dieback is very dk brown/black like the top of the cane on the first photo I posted. If I can find the other, I will post that too.

Fisherwoman, I hope your bushes will be ok. I haven't heard of a fungicide that is specific for it, except for suphur spray.

Thank you, Rosemary.

Here is some non-canker dieback:





Guess it's hard to see, but one thing I've noticed is that with regular die-back, the dead part comes to an abupt end with green continuing, but with canker, there is yellowing at the end of the canker, like more is to come.