Rose Rosette Disease
By Charles Shaner –
Consulting Rosarian - Shenandoah Rose Society
Rose Rosette Disease (RRD) is a viral-like
disease that is a danger to all ornamental roses. It is contagious and almost always results in the death of the rose.
It was thought that Virginia was free of RRD but there were two confirmed cases in the state in 2001 –
one in Albermarle Co. near Palymra and the other in Ben Lomond Old Rose Garden in Manassas
where 20 old garden roses had to be destroyed. I know of three confirmed cases in Virginia in 2002, one in Harrisonburg,
one in Staunton in Thornrose
Cemetery and the other in my rose garden. I had to destroy one Perfume
Delight and one Kardinal due to RRD. In 2003 there were numerous cases reported in the Staunton,
Rose Rosette Disease is carried by the microscopic
wingless Eriophyte Mite. These mites are carried by wind currents and can randomly drop into a rose. It is also thought that
the mite may hitch a ride on trucks traveling the interstate highways. Most infected bushes I have had were where the air
current caught a down draft (i.e. where the wind come over the top of a building or trees). Symptoms may not appear for weeks
or months. RRD is spreading unchecked through the wild rose population of the Midwest, South and Eastern
U.S.A. From infected wild roses, RRD spreads to cultivated roses.
The impact of RRD can be minimized if you
recognize the symptoms early and respond quickly. It is described in scientific literature as a potential biological method
of week control for ‘R.multiflora’. It was established with the help of the USDA and states in the 1930’s.
R.multiflora is a reservoir to harbor this disease and enable its spread. RRD can infect almost any rose on which the
mite lands and feeds.
RRD has a different affect on the rose than
other diseases. Instead of the cane dying, vigorous growth that is both rampant
and contorted appears. Growth may or may not be in the pattern of a witches broom. Death of the affected cane comes later. Diagnosis of RRD is confirmed Rose Rosette
Disease may be found in ‘nearby’ roses. Nearby means in the same bed, the same city block, the same county or
any place where a wind burst can deposit a dislodged infection-carrying microscopic mite.
In virtually every case of RRD I have diagnosed, I was able to find an infected R.multiflora
within 100 yards.
There is no one set of symptoms that can be
used to diagnose RRD especially in the early stages. Symptoms will differ from different parentage in different seasons and
at different stages of growth. The leaves and stems will be an ugly shade of reddish purple and so contorted as to be indistinguishable
one from another. If the rose has been infected for several months, a rosette will form at the end of the cane. Symptoms will
vary, but if you suspect a rose in infected, removing it quickly is a prudent action. Digging up and isolating the questionable
rose may also be considered although I have never been able to save a bush even with a slight infection. Once you have removed a bush, do not plant another rose there for two years. The roots left behind have been know to put up infected shoots as much as 18 months later.
Once a rose in infected, there is no cure!
There is a prevention and that is to spray every 10 days with Avid. Cygon2E was
the recommended spray but the EPA has pulled Cygon2E from the market. This is the only spray that will kill the mite that
carries the disease. There is no ‘organic’ control. If you think
you may have a rose with RRD, start spraying the surrounding roses every 5 days with Avid. RRD is contagious and can be spread
by you pruners. If you prune an infected bush, clean your pruners with the old