Roses infected at harvest cannot be marketed.
Rose black spot [Diplocarpon rosae]
Rose black spot - image 1
Rose black spot occurs only on roses. Plants are particularly at risk when there is poor ventilation and prolonged leaf wetness.
Pattern of damage
Irregular, dark, roundish to star-shaped spots on the top surface of leaves (Picture 1). The leaves yellow and detach upon being touched.
Fallen leaves must be removed from the rose growing area. Sufficient ventilation to ensure wet leaves can dry quickly. Preventative chemical treatment should be performed in order to stop sporulation.