| Rose rosette disease, also known as witches’ broom
of rose, is a virus that is spread by a very small,
eriophyid mite. The disease is limited to plants in the
genus Rosa. Its main host is the multiflora rose,
which is considered a noxious weed throughout
much of the United States. Interest in rose rosette has
been generated by the threat to garden roses and its
possible use as a biocontrol for multiflora rose.
Symptoms and Diagnosis
The earliest symptoms of rose rosette disease include
a red pigmentation of the underside of leaf veins
followed by sharply increased growth of vegetative
shoots, which are typically more succulent than
normal and colored in various shades of red. Leaves
will become deformed, crinkled, and brittle with
yellow mosaics and red pigmentation. As the disease
progresses, leaves become very small, petioles are
shortened, and most lateral buds grow, producing
short, intensely red shoots. The disease causes the
plant to be exceptionally susceptible to freeze
damage. Symptoms on cultivated roses are typically
less severe than on multiflora rose. Cultivated roses
show symptoms of thickened, succulent stems and a
proliferation of thorns.
Life Cycle
The disease can be transmitted by grafting and by an
eriophyid mite, a wingless mite that can travel
passively in the wind. Transmission typically occurs
between the months of May through mid-July.
Symptoms from new infections usually start
appearing in mid-July. In general, smaller plants go
through the disease stages more quickly than larger
plants. Small plants are usually killed in about 2
years, while a large plant may survive for five years
in a deteriorated condition.
Integrated Pest Management Strategies
1. Remove ornamental roses with symptoms. The
entire plant including the rootstock should be
removed and destroyed.
2. Plant ornamental roses as far away as possible
from known stands of multiflora rose.
3. Control the disease by controlling the mite. Pesticides such as carbaryl (Sevin), bifenthrin, horticultural oils and insecticidal soap may provide some protection when applied at weekly intervals during the months of June and July.
4. Using rose rosette disease as an IPM strategy: The
multiflora rose is an exotic invasive species that is
responsible for the degradation of millions of
acres of farmland and recreational areas. Using
the disease to control this invasive weed can cut
costs and be considered environmentally friendly
for reducing the amount of synthetic chemicals
used. However, the disease also affects cultivated
roses. One should be extremely cautious and
good neighbor-minded when it comes to rose
rosette disease. | 
