Do I have rose rosette disease? - Ask Extension
I have like 10-15 roses and they just all started showing strange growth. They started off great, then after the first flush, they started to produce ...
Knowledgebase
Do I have rose rosette disease? #872863
Asked June 12, 2024, 7:05 PM EDT
I have like 10-15 roses and they just all started showing strange growth. They started off great, then after the first flush, they started to produce fast growing shoots, bigger than the shoot they were coming from, lots of tiny thorns, and the buds at the leaf crotches started to grow just as fast as the terminal bud, then flop to the side limp. I have many more pictures, but they only allow me to list 3, but if you want to see more, contact me
Harford County Maryland
Expert Response
We're not yet certain what is causing those symptoms, though you are welcome to send more photos. (You can attach only three files per reply, but each reply you send, you can attach different images. The images in this first set seem somewhat muted or sepia-toned in color, so if you use a phone camera filter setting that affects color accuracy, please make sure it's turned off or not otherwise altering the color representation.)
Plant viruses can cause unusual growth, but the symptoms you describe don't quite match those for typical Rose Rosette. Did anything change in the area around the roses this season, like fertilizer applications being made or herbicide used nearby? Are all the roses the same cultivar?
Miri
Plant viruses can cause unusual growth, but the symptoms you describe don't quite match those for typical Rose Rosette. Did anything change in the area around the roses this season, like fertilizer applications being made or herbicide used nearby? Are all the roses the same cultivar?
Miri
My apologies, I’ve reattached and labeled the photos that I’ve taken.
The next 9 photos are of knockout roses. We have been getting lots of pests on these roses.
The next few are floribunda roses. These seem to be doing a little better, but still have strange growths here and there.
In both sets of photos, we used to have fantastic sized blooms and I haven’t changed feeding regimens. But now we get lateral buds that open before the terminal bud does, and they are all much smaller than before.
Thank you,
Brett
On Jun 13, 2024, at 9:58 AM, Ask Extension <<personal data hidden>> wrote:
Hello Brett,
Thank you for the additional photos. We do not see indications of Rose Rosette Disease in any of the images. Most appear to show simply spent flowers along with new growth, which is normally red or reddish on many cultivars. There is some roseslug sawfly damage, though it's very minor and does not require intervention at this point. Knock Out series roses are not pest-resistant (few roses are, if any), but they do have above-average disease resistance, at least to black spot. No rose cultivar has high resistance to all of the typical roses diseases.
Were the shrubs pruned back around March or so this year? If not, that might be contributing to some of the flowering behavior where terminal buds are not the first to open. (Do they ever open, or do they abort or die from some other cause, like thrips or Botrytis infection? If they die or abort before opening, then that explains why the second-tier buds take over and open instead.)
Has anything shaded the shrubs more than they used to be, like a nearby tree maturing? Reduced sunlight will impact flowering and plant vigor.
Although we do not see indications of this in the photos, since there is a fence line next to the plants, we wanted to add that herbicide drift can sometimes cause deformed growth on otherwise-healthy plants, if a neighbor used any lawn or other herbicide in recent weeks.
Are the roses mulched by bark doing better than those mulched by stone? The latter group might be experiencing greater heat stress from the reflected and retained heat of the rocks compared to the more temperature-regulating benefits of the organic mulch of just bark. Are the plants being monitored for watering needs? For most of last season, much of Maryland was experiencing drought, and we are currently abnormally dry in many areas again. Even if it doesn't cause blatant wilting, lack of water can cause plants to flower less abundantly or to abort flowers early that they do have (or they fade faster and don't last as long). High heat also often dwarfs bloom size for many rose cultivars. (For a few it improves flower size, but usually it's to their detriment.)
Miri
Thank you for the additional photos. We do not see indications of Rose Rosette Disease in any of the images. Most appear to show simply spent flowers along with new growth, which is normally red or reddish on many cultivars. There is some roseslug sawfly damage, though it's very minor and does not require intervention at this point. Knock Out series roses are not pest-resistant (few roses are, if any), but they do have above-average disease resistance, at least to black spot. No rose cultivar has high resistance to all of the typical roses diseases.
Were the shrubs pruned back around March or so this year? If not, that might be contributing to some of the flowering behavior where terminal buds are not the first to open. (Do they ever open, or do they abort or die from some other cause, like thrips or Botrytis infection? If they die or abort before opening, then that explains why the second-tier buds take over and open instead.)
Has anything shaded the shrubs more than they used to be, like a nearby tree maturing? Reduced sunlight will impact flowering and plant vigor.
Although we do not see indications of this in the photos, since there is a fence line next to the plants, we wanted to add that herbicide drift can sometimes cause deformed growth on otherwise-healthy plants, if a neighbor used any lawn or other herbicide in recent weeks.
Are the roses mulched by bark doing better than those mulched by stone? The latter group might be experiencing greater heat stress from the reflected and retained heat of the rocks compared to the more temperature-regulating benefits of the organic mulch of just bark. Are the plants being monitored for watering needs? For most of last season, much of Maryland was experiencing drought, and we are currently abnormally dry in many areas again. Even if it doesn't cause blatant wilting, lack of water can cause plants to flower less abundantly or to abort flowers early that they do have (or they fade faster and don't last as long). High heat also often dwarfs bloom size for many rose cultivars. (For a few it improves flower size, but usually it's to their detriment.)
Miri
My apologies, I’ve reattached and labeled the photos that I’ve taken.
The next 9 photos are of knockout roses. We have been getting lots of pests on these roses.
The next few are floribunda roses. These seem to be doing a little better, but still have strange growths here and there.
In both sets of photos, we used to have fantastic sized blooms and I haven’t changed feeding regimens. But now we get lateral buds that open before the terminal bud does, and they are all much smaller than before.
Thank you,
Brett
On Jun 13, 2024, at 9:58 AM, Ask Extension <<personal data hidden>> wrote:
Hello Brett,
We just received a reply from you that was a duplicate of the reply you sent on June 23. If you didn't receive our response from June 24, we can resend; or if you intended to submit a new question instead, please try sending it again since we didn't seem to receive it.
Miri
We just received a reply from you that was a duplicate of the reply you sent on June 23. If you didn't receive our response from June 24, we can resend; or if you intended to submit a new question instead, please try sending it again since we didn't seem to receive it.
Miri
