Rose buds develop normally but then fail to open and just turn brown.
Cause
This is usually caused by wet weather which ruins large, thin petals. It can also be caused by a bad aphid attack.
Harm
Flowers are ruined
Treatment
Organic – it is important to plant roses in an open sunny position as balling is most prevalent on plants that are in the shade, where the morning sun is not able to dry the buds out.