Rose Rosette Confirmation?

wichitagardener(6B)May 5, 2013

I have 5 Double Knockouts along the front of my house. Planted them in Srptember 2009. They are on the SE side of my home and have absolutely flourished. They are all around 6' tall and have put on a show each spring and summer.

However, I first noticed a few crazy looking branches last year and have just recently learned about Rose Rosette. If likes one of them is definitely affected, so I cut it down to about 4" stubs this morning. Below are some pics of one of the branches. There were probably about 5 or 6 branches that looked like this on a 6' tall by 5' wide specimen.

My questions:
Am I right in diagnosing this as Rose Rosette?
Is it a given my other Knockouts ( that are in direct contact with the rose took down today) will be infected?
Before I remove the rest of the Rose, is there any chance it will grow back healthy?

Thank you so much!

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More pics

    Bookmark   May 5, 2013 at 7:18PM
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    Bookmark   May 5, 2013 at 7:23PM
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catsrose(VA 6)

Yes, that is RRD. There is no chance it will recover. Dig it out, bag it or burn it. The other may or may not get it. I've had roses right along side RRD that never got it.

    Bookmark   May 5, 2013 at 8:30PM
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Thanks Cat. I will get the stump out in the next few days. Tough to bag that thing up, it was very large.

    Bookmark   May 5, 2013 at 9:47PM
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dublinbay z6 (KS)

Dig it up IMMEDIATELY. Everyday you wait, you increase the chances other roses may catch the infection.

Bag or burn the rose. Or it may pass the infection onto other roses.

You can cut the infected rose into smaller pieces that will fit into a strong garbage bag. Use several bags if necessary. Seal the bag or bags tightly.

Not a good time to delay or be careless about disposal when RRD is on the premises.

Make sure you dig out all the roots also--and properly dispose of them also.

Good luck.


    Bookmark   May 5, 2013 at 11:11PM
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Most certainly is RRD, however its not the end of the world. The virus is spread via the eriophyoid mite, and the mite itself does not fly or crawl but is blown by the wind. Remove the plants as quickly as possible and dispose of it. The virus does NOT spread by mechanical means (Touch, pruning etc.) so be careful in removal, but YOU can not infect the surrounding plants. The virus appears to reside in the crown of the plant so if you miss a few roots you will be fine, and it will not spread to surrounding roses via the root system.
The best means of preventing this disease is by pruning back all roses by 2/3's every spring. The mite overwinters in the top portion of the plant, and by cutting back every spring you significantly reduce the chance of infection. The pruning also helps the bloom power of KO's.
In the future early identification and removal of any canes showing symptoms will reduce your chance of losing the entire plant. Prune any infected canes back to the ground. If you do not remove the infected cane early and the affected cane overwinters it will spread throughout the plant.

Because it does not spread through the roots you may replant a rose in the same spot.

Good luck!

    Bookmark   May 6, 2013 at 8:35AM
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michaelg(7a NC Mts)

A tip about bagging rose canes: insert them top end first, because most roses have thorns that snag less that way.

    Bookmark   May 6, 2013 at 10:28AM
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The following was stated: "it will not spread to surrounding roses via the root system. "

H.Kuska comment: "The above is consistent with the statement by Dr. Jim Armine in the Q and A of the Rose Rosette Webiniar: "Q: Can remaining roots from removed roses infect a new rose planted in the same spot?
No. We proved that multifora roses do not make root grafts. I have not heard of any roses that make root grafts. The threat is when the few living roots emerge from the soil and become full-sized plants, they can then become infected." _Q-A.pdf

H.Kuska comment: A University of California Davis group has studied the spread of other viruses in roses and have reported that roses do make root grafts.

"Rose mosaic disease is often caused by Prunus necrotic ringspot virus (PNRSV) and Apple mosaic virus (ApMV). It is primarily spread by propagation; observations indicate a means of natural spread. Cuttings from two rootstocks, Rosa hybrida âÂÂDr. Hueyâ and R. multiflora âÂÂBurrâÂÂ, with and without virus were rooted and transplanted to pots. Viruses were: ApMV, PNRSV and a natural infection of ApMV + PNRSV. Treatment pots contained one virus-positive and one virus-negative plant in the same pot to permit root grafting. Control pots contained one virus-positive or one virus-negative plant; pots were arranged to allow stem contact. All virus-negative plants had a possibility of becoming infected by pollen or insect transmission. Dr. Huey included 60 virus-negative and 60 virus-positive control pots; and 120 treatment pots. R. multiflora included 20 virus-negative and 20 virus-positive control pots; and 20 treatment pots with ApMV + PNRSV. All plants were ELISA tested for 5 years. All virus-negative plants in control pots tested negative all 5 years. The percent of initially virus-negative plants in treatment pots that tested positive was 0, 5.3, 10.5, 10.5, 10.5 in Dr. Huey and 0, 12.5, 33.3, 46.7 and 46.7 in R. multiflora for years 1 to 5 respectively. All plants that became infected were potted with ApMV + PNRSV plants. Rose mosaic symptoms were observed only in plants with ApMV + PNRSV. This indicates that root grafting plays a role in spread of rose mosaic disease."


Here is a link that might be useful: Q ana A from webinar

    Bookmark   May 6, 2013 at 10:37AM
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Thanks for all of your replies and sharing your expertise. Here's a pic of the roses in a February snowstorm earlier this year.

I will be digging up the roots and examining the others tomorrow after work.

    Bookmark   May 6, 2013 at 10:22PM
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