History of Multiflora Rose
the 1930’s and
40’s, multiflora rose was promoted by the United States
Department of Agriculture Soil Conservation Service for erosion
control, strip mine reclamation, and use as a living fence
because of its dense, thorny growth habit. We now know that it
is a terrible weed, due to its ability to grow and thrive in
less than ideal situations and its ability to produce prolific
is extremely susceptible to rose rosette disease, and it kills
infected plants in about two years. As a matter of fact, the
disease is so efficient at killing multiflora rose that it has
been considered for use in controlling this pest. Unfortunately,
rose rosette disease can also infect our garden roses, including
hybrid teas, floribundas, miniatures, climbers, shrub roses and
old-fashioned garden roses.
Despite the fact
that rose rosette disease had been known here for so long, the
true identity of the causal organism was not known for certain.
It had long been thought that the culprit was a virus, but other
organisms such as phytoplasmas had also been considered. That
changed in 2011 when researchers at the University of Arkansas
and Oregon State University published their findings, confirming
that the disease is caused by a virus known as
An extremely tiny
(1/100 of an inch long and 1/400 of inch wide) eriophyid mite,
Phyllocoptes fructiphilus, spreads the virus from plant to
plant. They typically feed on shoot tips and at the bases of
leaf stems (petioles). These mites are wingless, and are blown
from plant to plant by the wind. The virus is also spread when
infected (but asymptomatic) roses are grafted to propagate named
varieties of roses.
disease is systemic and has been found in all parts of
infected plants except for the seeds. The causal agent is not
soil-borne, so roses can be successfully replanted where
infested roses have been removed. However, removal must be very
thorough so that no pieces of infected root are left behind that
There is still no
definitive laboratory test for the disease, so diagnosis is
based on a range of symptoms that vary from species to species,
even cultivar to cultivar, and with different stages of
Symptoms on multiflora roses include:
• New growth at
inappropriate times of the year.
• Rapid stem
• Bright red to
dark red mosaic patterns on the leaves. While many varieties of
roses have red-colored new growth, it hardens off to green. With
rose rosette disease, it stays red.
• Infected plants
produce numerous lateral shoots, known as witches brooms, that
create bunches of growth at the tips of canes. These shoots are
often bright red.
• Leaves are
smaller than normal, and may just feather out beyond the stem,
or they may be badly distorted. The distortion is similar to
symptoms of herbicide damage.
• Some canes
produce only sparse red and/or yellow foliage; others die and
Symptoms on garden roses include:
• Rapid stem
• Some cultivars
and species show red to pink colored leaves; others do not.
• Certain canes
produce an overabundance of thorns (hyperprickliness). These
canes usually die back in the fall.
• Short, deformed
canes grow, often red in color, and produce more buds than usual
and smaller-than-normal or badly distorted leaves. Again, the
distortion is similar to herbicide damage.
• Flower parts on
infested canes are distorted, sometimes leaf-like, while other
canes on the same plant produce normal flowers and fruit.
• Powdery mildew
becomes a problem on roses that are normally resistant.
• Symptoms come
and go. At times, the plant may seem to recover. Many garden
roses can go on like this for four or five years.
Protecting your Roses
Although there is
no chemical control for rose rosette disease, there are steps
you can take to protect your roses. First of all, monitor nearby
populations of multiflora roses - especially those upwind of
your garden - for the symptoms described above. Since they are
so susceptible, they can act as an early warning of the
disease’s presence in your neighborhood. If possible, eliminate
any multiflora roses growing within 300 feet of your garden.
Since multiflora roses do not die quickly from the disease, they
serve as a reservoir of infection.
The best course
of action is to remove and destroy garden roses that show any of
the symptoms described above as soon as you notice them. Be sure
to send them out with the trash or burn them rather than
Mites on Roses
mites is not as easy as it sounds – they are active from May
through September, they are not visible to the naked eye, and
they reproduce very rapidly, especially during hot, dry weather.
While there are
recommendations for commercial nurseries to control the mites,
the most effective materials are not available to home
gardeners. Since they are not insects, traditional insecticides
that home gardeners use may not control them. What’s more, those
insecticides can kill beneficial insects that keep other rose
pests in check, so you can wind up with an outbreak of another
roses carefully and getting rid of any that show suspicious
growth is the most practical course of action.
Pictures of roses
Rose prep for winter