Question
I live in Lincoln,NE and about two weeks ago noticed that five of my rose bushes had very long crimson canes which were covered with an extreme amount of little thorns(there were no other deformations).  I went to the local garden center and was told that it was a virus. They sold me a rose spray, was told to cut the canes, spray thoroughly and then fertilize well. Since then I have done a bit of research on the internet and believe that this may be rose rosette.  The pictures of rose rosette desease look very much like the canes that I cut except that they did not have the broom like appearance or any other deformation.  I then contacted the local university and e-mailed a professor who deals with plant pathology and explained my problem.  I was told that it certainly sounded like rose rosette and that I better dig up all my suspicious roses and spray all others with Cygon (dimethoate), dicofol OR bifenthrin (Ortho Bug B Gon Max Lawn & Garden Insect Killer).  I was able to find the Ortho Bug B Gon and just(today) sprayed my entire garden & lawn with it.  Now I am a little worried because I only see Cygon mentioned as an effective spray in various sites on the internet. Should I try to find Cygon and spray with it also? Is Cygon the only spray that you recommend?  Would it be unhealthy for the plants if I spray a second time with Cygon?

Thank you in advance for your time.

Marilyne Phelps

Answer
As you now know, Rose rosette is caused by a virus which is carried by tiny air borne mites. When a rose gets this horrible disease, it means that the mites are in your garden but they will only attack the roses. I am assuming here that you have dug up and destroyed the one that showed the problem. The other roses nearby will certainly contain some of these mites and will in time also get the problem. In the studies that have been done, it was only Cygon that was effective in killing the mites because it is a systemic chemical that is painted on the stems and when the mites bite they ingest the poison. Cygon has been taken off the market in the States and banned in many countries because it is a very nasty chemical even if it does the job well. So if you do find Cygon, spraying twice seven days apart, in my opinion is not the complete answer. These tiny mites can hide in many areas of the rose bush so I would spray but also to do a clean job, it has to be painted on the base of the canes of the roses. This then allows the sap to contain the poison.
There is no evidence of any other control for Rose Rosette except Cygon but because it is no longer available here is something you can do. Because it takes about a year for Rose Rosette to show up on a plant, it certainly means that there is a good chance that the roses  around or near the bush will have the mites. Keep a close eye on those roses and if you see any sign, then dig them up and burn them or put them in the garbage. The worst  is that you may have to replace a few of your roses but once the infected roses are gone, then it will be back to normal in the garden.