White Powder on Rose Canes

last year

last modified: last year

I googled powdery mildew but not sure if it is

Came across one of my Rose Standard.

The entire thing looked almost -pure white-. I had a glove a touched it. It was powderish. The rose is semi dormant - Bud eyes are pushing a growth out.

Is it powdery mildew. What do you guys suggest. I checked my shelf. All I have is a bottle of Sevin and Bayer...

I do know as of a 10 days ago, when I dormant pruned this, one cane was -oozing sap- out . Oozing enough to -notice- in the subsequent day seeing it, it was like a very slow leaking faucet. Could this trigged whatever - whiteout- we speak of.

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User

last year

After pruning, a fair amount of sap can flow from the cut ends and drip down the canes. As it evaporates it can leave a white residue. Because there are sugars in the sap, it can be a place for molds to grow as well. I believe its one or both things happening here.

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Mischievous Magpie (CO 5b)
last year
last modified: last year
Photos would be very helpful.
a1an
Original Author
last year
https://www.dropbox.com/s/18fltns2trr32lp/IMG_0946.PNG?dl=0
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My guess is its just some winter damage, and I wouldn't worry about it unless it persists a month from now. But do check some of the canes you pruned back. Is the center white? If not--if its brown--then you have cold damaged canes that need to be cut back until you come to white interiors. Try cutting back several inches at a time, until you get to the white. I'm not sure about Knock Outs, but on hybrid teas, they sometimes need to be cut back to 6 inches or so from the ground. I wouldn't think KOs would have that much problem, however. Good luck. Kate
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The spots pictured could be nascent canker, but are probably something else. Older rose canes change color in spring, and in the process often look specked and splotchy. Also blackspot fungus can make red spots on the bark--it's the main way that BS overwinters. (The spots do not damage the cane, but generate spores that will splash up to infect the leaves in spring. For this reason, severe pruning will delay the onset of blackspot for a few weeks.) There are probably many causes of red spots. True cankers may start with such spots, but develop into larger areas of dead bark, black or brown, usually with concentric zoning of two colors. Do an images search for rose stem canker. There are several kinds. Spores of fungal diseases are ALWAYS present in a rose garden, so sanitation efforts have limited value. It's possible to do a lot of damage with the pruning shears in a panicky attempt to prevent the spread of imaginary disease or a futile attempt to prevent the spread of a real one. (Fungal diseases take hold and spread mainly on account of very particular weather conditions.) I never prune out healthy wood because of red spots, and my roses have done well for decades. I don't prune out every actual canker, either. The rose's immune system will usually contain the canker until it becomes inactive. A rule of thumb you'll find in older rose books is to prune if the canker has girdled half the circumference of the stem.
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rosecanadian
last year
Is it scale?
Mischievous Magpie (CO 5b)
last year
Mealybugs, perhaps?
a1an
Original Author
last year
Scale did come across my googling. It did not look lke mealybugs
rosecanadian
last year
A1an, sorry that I can't be of more help. I've never seen anything like that.
rosecanadian
last year
Actually after looking at images on line...I think you have scale. So, if it is scale, I googled and you do this: For lighter infestations, gently remove scale with a soft toothbrush or cotton swab dipped in soapy water or 70% isopropyl alcohol. Test a small area first, as some plants may be sensitive. Check plants every few days and repeat treatment if necessary.

Then you have to keep checking in case they have reproduced.

Hope that helps...this is a gentle approach that won't harm the rose if we're wrong and it isn't scale. :) :) You can also cut off the canes if you'd rather.
a1an
Original Author
last year
last modified: last year
It's a terrible pic as it's zoomed in

But if you step back, the whole entire thing is smothered in *white*
a1an
Original Author
last year
last modified: last year
Not sure if the ISO will play well with the tender baby leaf coming from the buds.

I could probably use my blower and trying giving them a blow....but hopefully it won't displace them to another -victim-

I do use my blower all the time on the evergreen shrubs. It helps to dislodge any mites, etc...

Don't use it on roses as it just make the blossom head/petals gone @170mph blow force

I don't intened cut off the affected canes, cause as per the last post, Every cane, if not the bud union if not 2 inches going down the standard stem, is just pure -white- If I was to cut off the proposed -white-, it would literally just mean, I should just lop off it's head ;-/
Steve_M in PA
last year
I think it may be some kind of mold. Does it wipe off? Have you had freezing weather lately?
judijunebugarizonazn8
last year
I would say mold as well. In my experience, scale has a more “crumbly” texture and appearance. Peroxide is super for killing mold, but I’m not sure what is the best method of applying it in this case. I have diluted it and sprayed, but I wonder if a full strength wipe down might be better in this case? I would rinse well afterwards and hope for some dry sunny weather. Then again, I can imagine others might have first hand experience and can offer better advice.
rosecanadian
last year
Good info here!
a1an
Original Author
last year
last modified: last year
I just so finished washing the cars when I noticed it on my way walking past - still had my nitrile gloves on as it was a balmy 37F out. The white substance did come off with just a rubbing.

I think I will just give it a go and wipe it clean with a cloth. Knocking it off with a strong stream off the hose should do the trick as well I suppose, but I don't want this in the soil right........

Anyhow, interesting that even in this -cold temp-, it could develop mold. aka, it wasn't there 5 days ago. Maybe not even 3 days ago, But yesterday, every single woody part including graft + a few inches following down the stem of the standard had this white susbstance. So over the period of 2 days or maybe even just 1 day, the entire thing got covered.

I did point out 1 cane that was a dripping faucet after 1 day. The others did not appear to drip sap fwiw, and I did kinda look to see if there was, since the 1 cane I was aware about was a leaker..

Thx guys
rosecanadian
last year
We have some great experts here!
a1an
Original Author
last year
last modified: last year
I wiped it all off. All wood was looking clean.

She's white again the following day.

-I rewiped the canes all back down to wood and no white-

Let's see what happens overnight ?

Next suggestions, advice
rosecanadian
last year
Sorry a1an...I have no advice. Hopefully someone here will have some advice. :)
User
last year
Whatever it is, I recommend you not worry about it. I'm 99.95% certain this is nothing consequential.
a1an thanked User
a1an
Original Author
last year
last modified: last year
Thanks Paul. Are we saying it's also safe to hose it down and just let it get in the soil

Strong stream of water is alot faster than individual wiping. Individual wiping is more like 2 pass. 1st pass is to get it off. Then the second pass is with a clean towel to do a post wipe pass after wiping off the white stuff...

Rinse and repeat on all woody parts.
a1an
Original Author
last year
Should I be spraying anything ?

From the OP, I've done 2 consecutive wipe/clean and it's come back the next day. The folllowing next 2 days, I've also hosed it off. It looks clean after but the following day or the next following day, the white is back.
Steve_M in PA
last year
Maybe some neem oil or equivalent?
rifis (zone 6b-7a NJ)
last year
Paul Barden

5 days ago

Whatever it is, I recommend you not worry about it. I'm 99.95% certain this is nothing consequential.

a1anOriginal Author

2 days ago

Should I be spraying anything ?

From the OP, I've done 2 consecutive wipe/clean and it's come back the next day. The folllowing next 2 days, I've also hosed it off. It looks clean after but the following day or the next following day, the white is back.
a1an
Original Author
last year
For those on this thread, this white is not disappearing. I should wipe if again to see if it comes back....

I hosed it clean I think on Monday or Sunday....

It was raining all day yesterday.

Anyhow, a quick observation, but the white is back.
Steve_M in PA
last year
Is there any wound or mark visible in a place where you wipe the white deposit off?

Could you wrap some tape tightly around a certain spot where it keeps coming back? I am interested to see if the white develops on the outside of the tape, or under the tape?
a1an
Original Author
last year
Just circling Back. Paul, you were spot on. Even though multiple rinse/clean/wipe and it kept on re-appearing, it has finally subsided and the wood on it just remains clean.

White Powder on Rose Canes

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