I have no idea. You are saying they just died, with no symptoms?

Any fertilizer issues? Colored mulch? Weed-n-feed runoff from the lawn?

Witches broom-- also known as rose rosette disease (RRD)-- is showing up in large plantings of KnockOut like yours. Search this forum for more info.
Also inspect the roots of the dug-up roses for unusual appearance.
You might take a whole plant to your County Agent (be sure and bag it in a plastic bag & seal the bag tightly.)

Thanks for the replies. The only symptoms were the leaves dying. The roots looked normal. There was no weedkiller around. The odd thing was that the other roses in the row looked (and still look) normal. I did notice some odd leaf growth in some branches, which reminded me of virus infestation. If I get another death I'll take it to the Dept of Ag.

This has now happened to me. No witches broom or strange leaves just sudden death. Only the KO roses. Others, even tiny bands I planted, are doing fine. Strange. Almost seems like it is specific to the rose.

Yes, we have seen this dieback in a dense hedge of KnockOuts. None of the staff horticulturalists had seen it before or could identify the culprit.
We may be seeing these problems in KnockOuts because of the way they are planted, in big masses.
If we lose another one I'm taking it to the county agent, appropriately clothed in a body bag!
I used to be enchanted with the idea of rose hedges, but now am inclined to alternate roses in a mixed shrub border with shrubs of other species. That way if there are losses we'll have a less conspicuous gap.

If the original poster put his/her postal code on their member page, they are from southern Pennsylvania, where Rose Rosette is a serious problem.

On the row of Knockouts, did you see a lack of bloom?

Because Knockouts are so strong, often, from a distance, that lack of bloom gets lost in the massive bloom.

Then in winter, the RRD infected roses do not fully store sugars converted to starches and the next spring they are nearly dead. (That does happen in East Tennessee; in colder souther PA, there may be a similar problem. In Houston...?????)

The Penn Dept of Agriculture in State College may be able to help; at least one person there has known about RRD for going on a decade now.

It did not seem that there was anything wrong when first planted, they were growing and blooming. And then, sudden death. Perhaps this is a new ailment unique to KOs.

Lucille,

I don't mean to hijack a thread, but is colored mulch (like black mulch for example) a bad thing???

Maude

Yes there is a thread about it, you are hijacking so find the thread and we can talk about it there. I do not use dyed mulch so I don't think the rose deaths were due to that.

Here is a link that might be useful: Dyed mulch

Air pockets. This is a problem I have seen in assembly line bareroot pot-ups. I suspect thousands of KOs are potted this way.

The bare root is placed in a pot with a few inches of soil, then is quickly covered with a heap of soil, frequently leaving air pockets beneath the roots, and sent on down the line. A few moths later, when the plant is removed to put it in the ground, enough roots have grown to hold it more or less together and it gets planted. As the soil settles, however, the air pocket(s) gets larger. Eventually, the plant dies because the roots are not in the soil. If you stick a couple of fingers in towards the center of the root and meet little or no resistance and/or the soil collapses, this could very well be the problem. Ditto if you can easily pull out a plant that has been in the ground for two years.

That is an interesting theory and may very well be the case for many cheaply sold roses, but it did not seem to happen here. And for the deaths that do happen with bad potting, one would suppose that the death would be somewhat gradual as part of the root system would be in soil contact. These were sudden catastrophic deaths, pointing imho towards disease.

In East Texas, we are having similar problem. Happy groupings of bushes (Red Raz) with some bushes being 3 years old, full sun on a regular watering schedule suddenly look sickly. Over about a week one plant, surrounded by normal bushes will start to turn yellow and within a week it's dead. We feed them rose food and prune them to keep them a 5-6 ft. height.

Looks like others are having similar problems.
Thanks for suggestions.

A friend took a sample of one of my dying Knockout roses to the local agricultural extension service. They said it was a virus, transmitted by mites. This fits with my observation of the distorted vegetation growth and lack of any other obvious symptoms. I'm now spraying with a systemic product that says it kills mites.

Wait, there is "distorted vegetation growth"? If it looks like the photo's at anntn6b's eBook (linked below), then it is either herbicide damage (even if sprayed in a neighbor's yard, it can drift a long way) or rose rosette disease. Rose rosette disease is a virus spread by a mite, but a miticide won't kill this mite. It also won't rid your plants of the disease, the plants with the unusual growth will probbly have to be dug out and destroyed.

Here is a link that might be useful: Rose Rosette eBook

Thanks for your message, Diane. Is there anything one can spray to kill the transmitting mites?

No.

If there was, the people who manufactured it would be billionaires.

Jeri

I had one knockout after five years just die last fall. I dug it out and figured it a one off. Now, the summer following, one that had been close to it is showing all the same symptoms--yellowing leaves, some leaves drying completely, some canes dying. It had a normal bloom this past May.

Perhaps I just just give up and get rid of it, but it doesn't really address the cause.

Richard mine did the same thing. DEAD bushes and the ones next to it fin e. but later the one next to it started dying. I had a leafhopper of sorts, and lost 5 bushes out of 13. I sprayed Spinosid and then cut back EVERYTHING to 12 inches or less. The whole hedge. Its all coming back....it appears that bug was sucking the life out of the roses. LITERALLY. It wasnt really bothering any of the other roses just that hedge. I was at Burger King two nights ago and they have the same infestation of white flying leafhoppers on two of their knockouts (i could see them from 10 feet away there were so many) and the ko's were DEAD. Crispy....I warned them.....LOL

Leafhoppers transmit other diseases. A Polish study of a disease of Greenhouse roses reported that the disease was caused by phytoplasmas and leafhopper transmitted.

If you can find a rose that is just starting to sicken, contact TAMU and tell them the history and strongly suggest that they take the bush for study.

I wish I had known that before I #1 killed them all off and #2 pruned the bushes down to nothing....But they are coming back. These little suckers literally lived on the canes and sucked the "juices" out of them....I found them in my Belinda's Dream but they never touched my HTs or the other hedge along the other side of the parking lot that has Bonica in it. JUST the knockouts were affected but they were infested.

I did speak to someone at the local nursery who knew nothing about the symptoms I described on this board. She did admit to the issue of "witches broom" which she hears a lot about.

Well, I pruned them down and even then sprayed them with the spinosad. I'll post a follow up in a few weeks when I either have short dead canes or, hopefully, some healthy leafy growth.

I have had the "sudden death" visit several of my roses AND several of my roses have also had RRD (Rose Rosette Disease). So I know the difference, and the ones that experienced what I'm calling "sudden death" did NOT have RRD. And they were NOT Knock outs. (Two were Austins and one was Eden climber.) The "sudden death" ones just started dying back, one cane at a time, until the whole bush was dead. This happened mid to late summer.

Air pockets? I don't know--that is a new one on me, but it makes sense. I can say that the 3 roses that underwent "sudden death" were container roses (but from an excellent online nursery). Couldn't say if there was a connection or not.

Wish I had some answers. Unfortunately, all I have is more symptoms.

Kate

I have new growth on most of my Knockouts I cut back. I think two are not yet regrowing. The others are....so we shall see. that being said I had "sudden death" in three potted roses last year with nothing but, like you said, dead canes then dead rose. A Sexy Rexy, my Koko Loko and my Legends all did the same thing you are describing....in the middle of a healthy rose bed th ese guys just shriveled up...weird when you think about it.

We had 24 KO double red planted in April by a nursery we have dealt with for over 20 years. 3 plants were replaced because they didn't grow. They didn't die either, they just didn't do anything. Several of the remaining plants have very narrow leaves. Some have red leaves and canes but no thorns so I can't confirm RRD. Note neighbors have mature KO hedges with no apparent problems. I have another plant that has neither grown nor died. Any suggestions?

Couldn't attach 2 pics. This is the lazy rose that don't do anything. The whitish stuff is a surficant in Liquid Fence.

Any ideas? 4th KO to meet its demise... They are fine one day and croaking the next,

rodericky your photo with the two sets of leaves. The leaves on the right side is rrd.

I'm sorry I meant to say that both are rose rosette.