Why is there white powder on the leaves of my phlox plant?
By Raymi
Northumberland,
United Kingdom 
I planted the phlox a few weeks ago in a west facing border. I live in Northumberland on the coast.I first noticed the white powder when I was planting it and has steadily increased
15 Aug, 2009
Answers
Powdery mildew is mostly caused by the plants roots being too dry.
It would need watering daily as a newly planted item in the summer months.
If there are a lot of plants close together there isn't a lot of air circulating around them and this can double the trouble.
15 Aug, 2009
Sounds like powdery mildew - you need a fungicide spray to treat it with.
15 Aug, 2009