Rose Rosette Disease
As mentioned last week, Rose Rosette is a major viral disease for roses in Oklahoma. And thanks in large part to the popularity of the Knock Out line of roses, this disease is now something many gardeners in Payne County are having to deal with. The Knock Out roses are great plants, but like all things, they are best when used in moderation. When they first arrived in the trade several years ago, the Knock Outs were promoted as disease resistant and hardy in our area. And indeed, they were….for a while. As we’ve overplanted them, rose rosette has moved into this species of plant with a vengeance. You think we would have learned this lesson by now. Sigh.
The recommendations, as noted in OSU Fact Sheet EP-7329 Rose Rosette Disease, have generally been to remove all roses afflicted with this disease AND all roses growing in close proximity-close enough that their roots would intertwine. Note: This Fact Sheet has excellent photographs of the disease if you are not familiar with it.
I suspect these recommendations will continue to hold and that the long term prognosis for roses stricken by rose rosette is not good in that the plants will eventually fail. However, recent research suggests complete removal might not be necessary, at least in the short term. It is looking more like the virus is transmitted ONLY by mites and not by plant-to-plant contact as would be the case if the roots were growing together.
Before we talk about care options, we need to talk a bit about the vector (carrier) for this disease, the eriophyid mite. This mite is microscopic and can EASILY be transmitted by stem to stem contact, human (or animal) to plant contact, tool to plant, or even wind. We do not have any effective chemical control options for this mite. And before you ask-no, spraying insecticides “just in case” will NOT help. In fact, this could actually cause the mite build-up to become worse by killing off any beneficial insects that might be feeding on the mites.
I suggest cutting off affected areas of roses at least 6” or more below the lowest signs of damage and VERY CAREFULLY removing the damaged part of the plant. Try not to transfer the mites to healthy roses with careless handling. I suggest going straight to a trash container with each piece as it is removed. Remember, your gloves, sleeves and tools may now have mites on them so don’t work on healthy roses until you’ve cleaned everything up properly.
Watch the plants carefully for signs of further infections and be very proactive with further pruning if you see new symptoms. If the plant continues to fail, you’ve done the very best that you can do. Lastly, if you do have to remove a complete plant, I think it is a good idea to err on the side of caution and plant something besides a rose in its place.
For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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