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Rosette diseased knock-out roses #766889

Asked August 11, 2021, 12:13 PM EDT

My situation: We have 9 knock out rose bushes which all have some degree of rosette disease. The bushes are planted around the perimeter of the deck and have been blooming well all summer, despite being plagued by something eating the leaves. If we save any of the bushes we would transplant them. My research on rosette disease provided 2 basic answers regarding how to handle rosette disease: 1. Remove the bushes. Period. 2. Possibly save the bushes by cutting the diseased stems down to the base as soon as disease is detected. (it's too late for "as soon as the disease is detected.) I would cut the stems down now and do complete pruning in the fall. This advice said there is no guarantee the disease would be eliminated from the bushes and we would not know until next summer. I'd like to plant hydrangeas to replace the roses around the deck. I have a few and plan to purchase a few more. My questions are: 1. Do you agree with #1 or #2 above? 2. If we save some of the rose bushes and transplant them, can we do so now or should we wait until fall? Early, mid or late fall? 3. If we prep the rose bush beds for (sun-loving/paniculata) hydrangeas, can they be planted where the roses were? Can they be planted in the fall as well? Thank you so much for the opportunity to learn from your expertise!

Frederick County Maryland

Expert Response

Before you make any decisions we'd like to see some photos of your rose bushes, particularly any symptoms you think are Rose Rosette Disease. We sometimes find that this condition is a happy misdiagnosis.

You can attach photos directly to this reply and we'll have our plant pathologist weigh in.

As far as what's eating leaves, they commonly have problems with Japanese Beetles, which are easy to see, but also the larval stage of the Roseslug Sawfly, which are quite easy to miss. Here is our page on them: 

https://extension.umd.edu/resource/roseslug-sawflies-shrubs



Christine

Answered by theHome and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied August 12, 2021, 10:15 AM EDT
Thank you so much for your speedy reply Christine. Here are some pictures I took this morning of 6 of the 9 bushes.  I look forward to your further reply.


Thank you!
Marybeth Dahl


imageimageimageimageimageimageimageimageimageimage


On Aug 12, 2021, at 10:15 AM, Ask Extension <<personal data hidden>> wrote:

Dear mbdahl, here's the response to your question:


Before you make any decisions we'd like to see some photos of your rose bushes, particularly any symptoms you think are Rose Rosette Disease. We sometimes find that this condition is a happy misdiagnosis.

You can attach photos directly to this reply and we'll have our plant pathologist weigh in.

As far as what's eating leaves, they commonly have problems with Japanese Beetles, which are easy to see, but also the larval stage of the Roseslug Sawfly, which are quite easy to miss. Here is our page on them: 

https://extension.umd.edu/resource/roseslug-sawflies-shrubs





Christine



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The Question Asker Replied August 13, 2021, 1:46 PM EDT

Hello Marybeth,

Thank you for the photos. These plants are not exhibiting signs of rose rosette disease and the circled growth looks normal. Red-toned new leaf growth on roses is natural (the pigment is thought to serve as a sunscreen for tender young tissues) and is commonplace to many rose varieties. Clearer signs of potential viral infection would be clumps of notably disfigured, slimmer foliage, a drastic increase in stem thorniness, and other traits mentioned on this page: https://extension.umd.edu/resource/rose-rosette-disease

In either case, if you still wanted to plant panicle hydrangeas in this area, there is no risk to planting any after a rose is removed, and fall planting is perfectly fine.

As Christine mentions, you seem to have a little bit of roseslug sawfly chewing damage on the rose foliage, but we see so little of it (especially compared with the potentially heavy damage they could have caused) that treatment is not necessary and likely not worth the trouble.

 

Miri

Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied August 16, 2021, 10:33 AM EDT

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