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Dealing with roses that have rose rosette disease

I am not an expert. This is based on personal experience of having taken care of over 40+ roses (mostly knockout variety) in the past 5 years. All of my roses, and my neighbors, have fallen victim to the uncommon rose rosette disease. This is what I learned...

What is Rose Rosette disease?

Rose rosette disease is a condition that causes roses to grow strangely deformed stems, leaves, and flowers. The disease itself is a virus, but it requires a very tiny mite called an eriophyid mite to transfer the disease between plants. Eriophyid mites are so small that they can only be seen under strong magnification. The mites settle in to feed on the rose and transmit the virus into the vascular system of the plant.

Infected roses can be confused with scorching, fungal, pollution, or over feeding. No variety of rose is immune. Especially the "Knockout" variety, that advertise to be disease resistant.

In the photo below, you can see the difference between healthly knockout roses, versus one infected with rose rosette disease.

How does it spread?

The mites can be spread by touch, or wind. This means that if a person, animal, tool, or weather can transfer the mites from an infected plant to a non-infected plant. Even leaves from infected rose can travel to your neighbors roses and infect them. Which is what happened to me the first time, and possibly the second time. Once the mites have transferred, the probability of infection is inevitable.

Control

Once a plant has the virus, there is no saving it and it is highly contagious. It will continue to grow deformed until it eventually dies, which could take a couple of years, depending on how often you prune. The more you prune, the faster it dies, because everything that grows back after infection has a strong chance of growing back deformed.

Replacing the rose in the same season will not work as well. The infection or existence of mites can still be in the trimmings and sheddings on the ground, as well as the existing roots(not confirmed). It is recommended by experts that you wait at least 1-3 years before planting another rose in the same location. This is to ensure the mites have left the area, and any existing roots have died.

First indication of infection

When your roses start showing signs of having bumpy leaves, prune the area ASAP, place it in a bag to prevent further cross contamination, and treat for mites & fungi in an attempt to save it. Bumpy leaves can be caused by a variety of insects & fungi, but it is better to be safe than sorry. Eventually, they will turn yellow as if suffering from hot dry weather. Fungi infections can cause this effect too, always check your roses for white/black spots and treat it at first signs(before they turn yellow), so you don't confuse it with rose rosette disease.

Killing the mites with treatment

Not just any mite control chemical will do. At the time of this article, I have only found one mainstream product that kills the eriophyid mites and that is Sevin Dust.

You can do your own research as to what products kill these pests, here is a list of chemicals that work against eriophyid mites: Avermectin (Avid), fenpyroximate (Akari), pyridaben (Sanmite), endosulfan (Thiodan), chlorfenapyr (Pylon). Dicofol (Kelthane), bifenthrin (Talstar), and carbaryl (Sevin). No known organic treatment works.

Keep in mind, that once your roses have become infected, treating it for mites will not save it. Technically, the virus kills the roses, not the mites.

Testing for infection

A standard test you can do is clip 2-3 barked steams and wait for regrowth. If the regrowth has deformed & retarded growth, it is certainly infected. This virus is the only one of its kind, and cannot be mistaken for something else.

Tips for replacing

Some folks have had success within one year when replacing the roses. This is what they did: remove the rose with as much as the roots as possible. Then remove a few of the surrounding plants if applicable. Rake the area and dispose of material(best if burned). Apply Sevin Dust(power, liquid, or graduate form) to the area once a month, for a minimum of 6 months. Finally, in the early upcoming fall, plant your replacement roses and treat with Sevin Dust.

I tried replacing by cutting down in the fall, used wrong treatment, and planted in the early spring. This did not work for me. I do not know if it was because I did not properly treat, or if it was because my neighbors house still has infected roses and the weather transferred the mites to mine.

This year I removed them in the fall, treated all through spring & summer, and will plant in the upcoming early fall. I will update this article next year if this method worked for me.

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