Hi this may help.
---------------------------------------------
THRIPS
If the petals are blackened,with mottling and distortion, this
is likely to have been caused by the Rose thrip, Thrips fuscipennis.
Thrips, also known as Thunderflies, are small, narrow
insects just 2mm long, slightly wider at the front end. They tend
to jump away when disturbed,though you can usually confirm
their presence by shaking an affected shoot over a sheet of
white paper. They are more of a problem in a hot summer and, if
you notice a lot of damage early in the season, spray with a
general-purpose insecticide to reduce future damage.
ALTERNATIVE
I have used 2 spoonfuls of white Vinegar to one gallon of water
but only with limited success.
