Symptoms
Symptoms are yellowing leaves surrounding angular areas which can vary from green islands, to purple or dark brown lesions. Severely infected leaves may fall, often resulting in rapid defoliation and consequent reduced plant vigour. In addition to the leaves, the fungus also infects and causes purplish discolouration of stems, pedencles, calyxes and petals.
Sporulation occurs on the underside of the leaves and spore masses are initially white but become light grey with age. Sporulation can precede the appearance of symptoms.
Management
Greenhouse sanitation, adequate ventilation and fungicide applications.
Downy Mildew Life Cycle
