Blackspot on Roses. - Black Spots
on Rose Leaves
Whilst there are some Rose varieties that are
very susceptible to Blackspot, Black Spot. This disease (fungus) it can attack
most varieties given the right conditions.
Ironically, clean air allows the disease
to take hold, whereas the old industrial atmospheres which were
generally loaded with sulphur, controlled Rose Blackspot to a large
degree! South West UK and S Wales are said to be the worst areas for
The sure signs of Rose Blackspot, are the rounded black
spots on the leaves which themselves are normally surrounded by yellow
areas. These yellow areas spread outwards which result in premature leaf
drop, and can be so damaging as to affect the stems with dieback if the
black spot is not controlled.
Leaf infection is the first sign of blackspot, but in severe
infestations, this can spread to rose leaf buds and then stems.
The actual infestation start quite early in the
year, but does not start to show through to any extent until late June or July -
depending upon season and also the atmospheric conditions. Warm damp conditions
are ideal for the spread of Rose Blackspot.
There is no cure for the affected leaves, though
a spray of a rose fungicide or combined rose spray such as Multirose will halt
the spread. Infected leaves should be removed and burned. Rose leaves affected
with blackspot should NOT be put on the compost heap - or even into your
As with many things, Rose Blackspot - Black spot
- is best prevented with a preventative spray early in the season - before the
foliage starts to show through even. Also spray the ground around the rose
bushes at this time.
Most garden roses are prone to this disease, and
much depends upon cleanliness for its successful control.
With roses that are susceptible to blackspot,
then spraying every two weeks might be necessary.
Hard pruning in the spring - and burning of all
pruning material is useful with those varieties of roses that regularly get
blackspot - black spot. A feed with a high potash content will also help to
allay the disease. This should be carried out early in spring in order that the
rose plant may take the potash in as a preventative.
By David Hughes -