Knockout rose with blackspot ?

Question

One of my Knockout roses developed blackspot this season. I removed the affected leaves and cleaned up the fallen ones. It is showing new growth :) My question is, how do I prevent it next season?

I drip irrigate in the AM so I haven't gotten water on the leaves and certainly the plant wasn't sitting overnight with water on the leaves. I can't imagine how this happened. The plant gets morning sun. My other Knockout rose planted just down from the sick one is as healthy as a horse. I bought the sick one at Wal Mart. Did maybe they do something that would have added to it?
I had it for about three months before it developed the blackspot.

Thanks for any input :)

Answer 1

Wal-Mart waters over head and their roses pretty much always have black spot. However, the beauty of the Knock Out Rose is that it is an Earth Kind rose and according to Texas A&M they will recover you don't have to do a thing to them. I have two Knock out roses and this Spring my area experience a monsoon which lead to black spot on just about all of my roses including the knock outs. I treated all the others, but I left the knock outs alone to see if they truly would recover on their own and they did. You can treat them with a fungicided like Ortho rose defense if you like, but it's really not necessary. Here is the site if you are interested in learning more about the Earth Kind roses and there are a lot of them. They are supposted to be drought tolerant and disease resistant, requiring nothing in the way of fungicides or supplimental watering. Texas A&M is also interested in people who have Earth Kind roses participating in a study and all you have to do is nothing to your roses except let them do their own thing.
Earth Kind roses:
http://aggie-horticulture.tamu.edu/earthkind/EKRoses/index.html
Earth Kind rose list:
http://aggie-horticulture.tamu.edu/earthkind/EKroses/EKbrigaderoses.html

Good Luck

Answer 2

Knockout roses are black spot resistant, not immune. If you have ever seen the quality of care provided a rose in the possession of WalMart or any of the other Big Box stores you would not need to ask this question. I'm certain that the fungal pathogen came home with you from WalMart and your rose was susceptible due to the stress of its care (or lack thereof) at WalMart and transplanting. Your cultural practices are right on for reducing the inoculum for next season. A non-toxic fungicide that works for the prevention and cure of black spot is a spray of milk. Use skim milk (1 part) to 9 parts water. Spray every 7-14 days when weather conditions (wet leaves for 7 hours or more) are right for the development of black spot.

Answer 3

Knockout Rose Diseases

Answer 4

Knockout Roses are pretty bullet proof.

They want full sun, lots of air movement, not much water or fertilizer. They really like well drained, organic soil.

No matter what, they will still get a few problems.

Now go drink a beer and worry about something else.

Answer 5

Hi! I don't know why they developed blackspot. I can only tell you my experience with them. I bought 4 double knock out roses for my front yard. 2 red and 2 pink. While they all flower, they also get ate up by something, because there are holes all throughout the leaves and it looks awful! They always come back, but I thought they were supposed to be pest proof! Also, one of the pink ones didn't grow right. The rest of them are 3-4' tall, but it doesn't even reach 2'. So it doesn't match up to the other ones. I'm going to be taking it out and replacing it. I feel your pain, it's a shame you have so many!

Answer 6

Black spot is a hard one. It is inerrant in the soil here in NC. Basically it is a fungus that lives in the soil. There are several good products (fungicides) for roses that you can use while the bush is in leaf. For preventative maintenance try cutting back your rose bush AFTER it has gone dormant, by about 1/3. Be sure to remove all of the cuttings from the area as they can contain the fungus spores. Spray the ground around the rose liberally with dormant oil, and make sure to get a good coat on the bush itself. Lay at least 4 inches of fresh fungus free (commercial bagged) mulch around the base of your Rose and out from the base at least two feet in all directions. When your first foliage comes out in the spring be sure to spray them with a good fungicide. and keep spraying them about every three weeks or so, or when ever you see the first tiny spots starting to appear, if they appear.

This is not a cure all, but I have used it on my roses for the past several years. They used to loose all their leaves to Black Spot, not they keep most of them all year long and bloom beautifully, And there is the added benefit that the mulch makes them require less watering.

One last note, if you have already mulched the bush, please remove all of he old mulch before adding new sterile mulch. Black Spot fungus lives in the soil and mulch, so you want to make sure to get rid of the old.

Answer 7

During this past summer I sprayed my roses weekly and kept them trim in a way that they had plenty of air space between the branches. I would completely remove some of the branches from the center. It was a highly successful season for me. I have about 25 plants of various species.

Answer 8

Mix cr500 and a Well Lit Gardens answers and you will have the perfect answer.
You need more light, well drained soil, and for heavens sake QUIT buying BOX STORE crap, and invest a little money into the GOOD stock local Garden Centers sell.
Then have an inexpensive beer!

Answer 9

Roses should get plenty of water,at least 6 hours of sun,plenty of air movement(i.e. make sure air can get to all the plants to prevent high humidity around the plant) and day and plenty of food.My suggestion would be to give it a big feed.

Answer 10

rose in general is very substitutable to many fungal diseases. Consider keeping them on a fungicide treatment plan next year.
good luck