Funghal disease that pops up late summer caused by poor airflow & overcrowding of crops
White, powdery dust and blotches appear on leaves.
Then causes leaves to darken and spots become more defined
Powdery Mildew is an annual occurance when plants affected hit their productive phase..
Increase air circulation.
spread out plants as much as you can, and keep foliage dry to begin with
Break the first few leaves you see with mildew, and dispose in household rubbish
Bicarbonate of soda solution can help if sprayed on plant (1 gallon of water, 1 tablespoon baking soda, 1 tablespoon vegetable oil, 1 tablespoon dishwashing liquid.)