Appearing as brown bruising on the petal mainly on white and pale colours. A multitude of extremely small insects swarming on the petals. Blooms don’t open, petals stick together.
No easy to remedy. The insects blow in with hot north winds from dry paddocks and dry roadside grasses in country regions. Mostly effects the early spring flowers, but new growth will follow with clean petals. No cure, if spray one day fresh insects the next.
Very disappointing to see the damaged flowers, particularly if roses only flower in the spring. This is one of the rose problems which although unsightly is best to just accept for it is no major problem and very short lived.