Mites have a Mighty Impact on Roses – and It Ain’t Pretty

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I have been seeing more reports and articles regarding a disease called Rose Rosette Disease (RRD) in my gardening trade magazines, and thought it worthy to note on my blog for those unaware of this disease in roses.

RRD is not new, and mostly affects the weedy multiflora roses (Rosa multiflora) which is particularly susceptible to RRD.  But now RRD is being discovered in production on cultivated roses in more states.  Three confirmed cases were reported in Florida in nurseries located in the counties of Gadsden, Alachua and Levy per a recent article in Nursery Management (see link below).

Roses affected with RRD will exhibit particularly odd growth – you may see excessive thorns along the stems, elongated shoots, deformed blooms, and weird red growth (similar to witches’ brooms) from the growing tips of stems or branches.

It was noted all of the infected plants in the Florida cases belonged to the Knock Out series.  This made me think, “Uh-oh” because Knock Outs usually don’t experience lots of problems, and is a type of rose I’ve recommended to the beginning gardeners interested in having a rose bush in their landscape.  Knockouts tend to be reliable, easy, and disease resistant.

RRD is a virus disease transmitted by a tiny mite.  After the rose starts to look distorted in places on the plant initially, the disease will take over the entire plant and lead to the plant’s death.  The mites can be carried from an infected plant to a healthy plant by wind (and RRD is also transmitted via grafted roses).  While the mite is tiny and a critter (not a true insect) invisible to the naked eye, it has a mighty impact as it transmits the disease from plant to plant.  No one wants to see their treasured roses deformed and if you haven’t heard of RRD yet, you are probably wondering as you read this what you can do if it appears on your roses.

Some references indicate you should cut out the bad canes infected by RRD and toss (destroy) them.  If the problem is prolific in the plant, you should dig it up with the roots, bag it and toss it all together.  This is not a soil born disease, so it should not affect the spot where the rose was growing, but if you happen to have the weedy and noxious multiflora roses near your property, you may want to move those out since RRD can spread from the multiflora roses to your cultivated roses.

I’m not an expert on RRD or roses for that matter, but I felt it worthwhile to give a brief note about RRD on this blog due to the confirmed cases in Florida.  While this disease has been around for a long time (since 1941) and is occurring in several other states, it appears to be creeping into new areas.  Hopefully it won’t show up in your gardens.  Most infections occur in the spring, so this is something to look out for or at least be aware of if you aren’t already with spring fast approaching.

For detailed information, it is best to visit the experts (see links below), or ask your local nursery experts about it when you visit the nursery this season.  You can find a few experts discussing the RRD problem via video links at the AmericanHort website along with detailed information sheets about the rose rosette disease.  Photos of the symptoms caused by RRD can be found via the links listed below as well.

For details, visit:

Useful Links:

Missouri Botanical Garden
Michigan State University
Virginia Cooperative Extension
Alabama Cooperative Extension
NRCS (Control of Multiflora Rose)
Utah Pests fact sheet (Eriophyid Mites)
Nursery Management (Florida cases)

Written by Cathy Testa

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