Blossom blight :  Phytophythora palmivoras

Symptoms

• The disease appears as light brown, irregular, water soaked spots on flower stalks and petals.
• The spots increase rapidly and coalesce with one another and form distinct depressed lesions. 
• Under humid conditions the infections become severe involving the entire flower head and resulting in blossom blight and stalk rot.
• The disease is favoured by drizzling rains and cool moist weather. 
• The fungus is soil-borne and the infection starts from the base touching the soil.

Management

• Use of disease free soil for cultivation reduces the disease incidence. 
• Affected flowers should be collected and destroyed.  Excessive watering should be avoided.

Image source:

http://www.plantmanagementnetwork.org/pub/php/research/2011/daisy/