The latest on rose rosette virus

While the individual flower looks great, rose rosette is killing off branches around it. It’s only a matter of time.

It’s a disease that was first found in wild roses east of the Rockies more than 80 years ago. It had been observed across the entire country within 20 years, but it wasn’t until around 2010 that it became an every-garden threat in big parts of Texas. Currently, gardeners in the DFW Metroplex have gone a decade without seeing more than a handful of normal-looking rose beds in bloom.

Lynn and I have walked past this poor plant a couple of times weekly for the past several years. RRV is taking it down. Click image for larger view.

Here are the critical facts…
Rose rosette virus (RRV) is spread by the mouthparts of the microscopic eriophyid mite Phyllocoptes fructiphilus.

The mite does not crawl from plant to plant, but instead perches on one plant waiting to be caught in the wind and blown to the next.

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Although the mite must feed on an infected plant for 5 days to be able to carry the disease, it is then able to infect a healthy plant within just one hour of renewed feeding on its new host.

RRV only affects roses.

The clubby, distorted growth of rose rosette virus-infected plants is very obvious here. Click image for larger view.
And the distorted growth is even more obvious as these stems deteriorate and die. Click image for larger view.

Symptoms of infection of RRV include clubby “witches’ brooms” of new growth; vastly excessive thorns on some stems; extremely vigorous “bull” canes on occasion; discolored or distorted buds that often fail to open properly; mosaic-patterned leaves; and, in time, dieback of twigs and then loss of the entire plant.

This planting looks healthy, but to a trained eye, RRV sticks out like a sore thumb. Note the strong “bull cane” in the lower right corner.

What to do now…
Before your roses go completely bare for the winter, inspect the plants closely. If they show any abnormal signs of growth or dieback that might indicate the presence of RRV, it’s probably best just to remove the plants entirely (including roots). Put them in a plastic trash bag and send them to the landfill. Do not compost them, and do not take them to the nursery for confirmation. They don’t want them near their rose plants.

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In theory, you can replant roses immediately if you have removed all parts of the old plants. I would limit the numbers I planted, and I would probably plant them in another part of my garden away from the old site, just because I’m superstitious.

This plant will be much farther downhill by spring.

Separate your new roses to lessen the chance of the mites blowing freely between plants.

Choose healthy specimens that you know are not infected when you stop by your local nursery come spring.

You might even opt to switch over to perennials, robust annuals or even dwarf crape myrtles as replacements until research finds us resistant roses. I’m especially fond of the “Petite” series of crape myrtles. They’ve been around 60 years, but I haven’t seen any others that are as good in the interim. They come in all colors, although you may have to search to find them, especially now in their “off” season.

Do some more research…
There is plenty to read online on the subject of RRV. Google “latest findings on rose rosette virus.” Unfortunately, what you won’t find is the magic solution. There’s still lots of work to be done.

Here is one of the best reports in terms of information and illustrations. It’s from Barbara Gregerson of the Michigan State University Extension Service and it’s less than 10 weeks old.

Posted by Neil Sperry
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