Roses infected with rose rosette develop a dark, purple-red discoloration that can be confused with new growth. There is no treatment for the virus, which is spread by wind-blown mites. David Pulliam dpulliam@kcstar.com
Roses infected with rose rosette develop a dark, purple-red discoloration that can be confused with new growth. There is no treatment for the virus, which is spread by wind-blown mites. David Pulliam dpulliam@kcstar.com

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KC Gardens

Roses are under siege from an incurable disease carried by wind-blown mites

By Dennis Patton

Special to The Star

June 30, 2017 08:00 AM

UPDATED June 30, 2017 08:00 AM

Roses are one of the most popular landscape plants. Easy-care roses, such as the popular Knock Out variety, essentially reinvented the plant. The once fussy and hard-to-grow tea rose suddenly became new again.

There’s no other flowering shrub in the landscape that can provide as much impact for such a long period of time. As such, roses have been popping up in just about every yard and commercial planting.

Unfortunately, all good things must come to an end. Because of a disease known as rose rosette that’s spreading throughout the country, many of our beautiful roses are under attack.

Rose rosette is spread by small, wind-blown mites that carry the virus. Where the mites move and land is really just up to chance, but the more plants they infect in a given landscape, the more likely the disease is to spread to healthy plants. Removal of the infected plants is the key to helping control the disease’s spread.

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The symptoms of rose rosette are not always easy to identify. Infected plants develop a dark, purple-red discoloration that can be confused with new growth. And diseased growth can develop numerous small thorns that cover the stem.

The disease also creates what is referred to as a “witch’s broom”: a mass of branches that all arise from one growing point. Flowers become misshapen and don’t open properly. In the later stages of infection, canes of the plant die as the plant is weakened.

Because rose rosette is a virus, there are no ways to control it once the plant exhibits symptoms. The only true method of control is removal of the plant.

The other bad news is there are no treatments to prevent the spread. Insecticide sprays are ineffective. This problem is an epidemic in the Kansas City area, and anyone who has a rose bush should be on the lookout.

There are proactive practices that can help stunt the spread of this disease, however. As stated, make the tough call and remove infected plants. Pruning out the infected parts only delays additional symptoms from developing and provides a source for mites to spread to other plants.

You can also plant roses farther apart in the landscape so foliage is not touching. When the foliage touches, it’s easy for mites to crawl from infected to healthy tissue. When the plants are more isolated, the wind must move the mites.

Rose rosette isn’t transmitted by pruning shears, but it’s still a good idea to disinfect your shears when moving from one plant to the next as part of good hygiene. It’s also not transmitted by old roots left in the ground, so an infected plant can be removed and a new rose can be planted back in the same location. Keep in mind that the new plant can still become infected through the mite movement, though.

Roses are garden-worthy plants in the landscape as long as you know the risk. While this disease is fatal, roses can still grace your garden if you’re proactive and use smart planting.