Those
unsightly and damaging black spots on your rose leaves, commonly called “blackspot”,
are caused by a wind borne fungus also known as “Diplocarpon rosae”. You will notice this fungus when your rose
leafs have a black round spot, eventually turning the leaves yellow and causing
them to fall off leaving you with an unsightly looking rose bush. This disease can be devastating to rose
bushes and if severe enough will weaken your bush and blooms.
Blackspot is
especially prevalent in climates with a lot of rain or high humidity. Blackspot cannot be cured but there are
methods to control the spread of this damaging disease.
One way is
to remove the areas affect by black spot and be sure to pick up any leaves or
other parts of the plant that still harbor the fungus or it will possibly
spread from the fallen leaves.
Using
fungicidal soap or Sulphur in dry weather (as rain will rinse these off) is one
solution to help prevent further damage.
Both of these can be obtained at your local nursery. There are also natural solutions that may
help slow blackspot disease.
According
to horticultural professor Jeff Gillman, a spray composed of one part milk and
two parts water will help when applied weekly.
The best
prevention for black spot disease is to space out your roses when planting to
allow air circulation. It is also best
to water your roses using a drip or soaker type hose on a day the sun will dry
out any possible moisture on leaves.
