help with black spot on roses

last year

I have a few roses I grow in containers. Two are knockout roses from Home Depot, one is a mini rose variety. I noticed this year that the most established of the roses started having spots (darker green on leaves that turned darker) a few leaves and first but spread quickly. I read that it’s black spot. I tried spraying with neem oil and fungicide several times. I also removed the leaves that seemed to have damage and pruned (after it had its first blooms). Now I’m seeing some leaves fully drying out. Is there anything else I can do? Is it something else? Here are some pictures of how it looks now (more pictures in first comment). Any advice would be greatly appreciated. Would like not to throw it away…

Featured Answer

Moses, Pitt PA, cold W & hot-humid S, z6

12 months ago

last modified: 12 months ago

Me,

Heather hit the nail on the head. Knock Outs, if given good care, need no spraying for fungal diseases. They do get all the insect and mite maladies like any other rose, but disease wise their foliage is just about bullet proof.

I believe your problems began with a rose under much stress. Under extreme stress a Knock Out will black spot. Your foliage looks like it was over sprayed, and the bush itself is so bad off I would not spend the time or money trying to nurse it back to health. You have to look at the economics. The safety issues of misusing chemicals is also a factor.

Get a new Knock Out. That's a Double Red, right. Pot it in the right sized pot. Use top grade potting mix. Fertilize carefully. Osmocote is fool proof and success guaranteed. Site it where it is not environmentally stressed. Then you should have success.

Moses

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Comments (14)

Me 1 (zone 7b NY)
Original Author
last year
More pictures
0
Moses, Pitt PA, cold W & hot-humid S, z6
last year
last modified: last year
How big is the container, gallon wise, that contains your Knock Out? You've had the Knock Outs two years now?

Mini roses get every insect and fungal disease that comes down the pike. What is your mini's varietal name? In what size container is it growing?

Moses
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Heather RR (PNW 8b)
last year
Some of these leaves look burnt and dry, fungicides and neem oil can cause this if applied incorrectly.

How is the drainage in your pots? If the soil isnt draining well that can cause problems as well. I second Moses and his question about pot size, it might be time to size up your pots.
Me 1 (zone 7b NY)
Original Author
last year
I think pot size are ok for the plants, especially after I’ve pruned them smaller. I’ve replanted the year I got them into bigger pots they needed. Does container size impact resistance to black spot? Is that the main issue?

The roses are going down so quickly,
within days…went from a few leaves with a problem to the pictures above to now 90% of leaves having problems …. What am I doing wrong????
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Me 1 (zone 7b NY)
Original Author
last year
How do I apply fungicide correctly? I’ve been spraying those when I noticed the problem as often as I could. Was that supposed to be differently? I tried not to apply during mid day when in full sun, more afternoons and evenings
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Me 1 (zone 7b NY)
Original Author
last year
The problem is spreading… am I better off doing nothing? Not spraying? The mini rose seems to do better than all but it’s further away. I don’t know the variety (got it in a small pot at a store and replanted over the years info bigger ones) but now it’s also developing this problem….
0
Me 1 (zone 7b NY)
Original Author
last year
Here are pictures of mini roses, leaves are starting to show same symptoms as the knockout roses…
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Me 1 (zone 7b NY)
Original Author
last year
For reference this was my knockout rose last May. How do I bring it back? Thanks!
0
Me 1 (zone 7b NY)
Original Author
last year
It’s now in a bigger pot
0
Moses, Pitt PA, cold W & hot-humid S, z6
last year
last modified: last year
What is the volume size, in gallons, of the pot you intend to grow the sick Knock Outs in now? The exact answer to my question is pivotal to further advice I can give.

As Heather pointed out, you have been OVER CURING with spraying to attempt to restore the bushes, when pot size is at the root of their problem.

Moses
Heather RR (PNW 8b)
last year
I grow lots of roses in pots (currently over 100 while waiting on construction projects) and the key to keeping them healthy is pot size and regular feeding and watering. A knockout rose is normally able to fight off blackspot but when stressed by a small pot or lack of nutrients it will succumb.

I don’t spray but if I did I would follow the instructions on the bottle. The burnt leaves are a sign that you have been over spraying. I would stop spraying, hose down the plant to get rid of the neem oil and remove the worst of the burnt leaves. If you havent already, start a fertilizer program. I use fish emulaion for my pots but Osmocote is a great easy option, my dad uses it for his potted hybrid teas and they always look fabulous.
woodrose
11 months ago
Stop spraying ! You're killing your roses by trying to cure them. Keep them watered, fed, and hope for the best.
Vaporvac Z6-OhioRiverValley
11 months ago
To address a comment you made above, 1 must apply fungicides before problems. It prevents problems it does not cure them.