Posted: 02/07/2014 at 00:16
Keep plants moist....don't let,them dry out and stress. ,asters,polemoniums and others are prone to mildew in hot humid weather. Some vsrieties are more resistant,than others,,for example, in the aster family so check out those reputed to be better. Monardas too....some will always get mildew whilst others may not.
For me, treatment is the same.....cut back every stem to base, spray with fungicide, feed and water well. Then another good watering next day then a mulch.
Scabious is susceptible too. To avoid mildew I cut back ..late Chelsea chop I guess....before signs of it if I can and this energises the plant to produce fresh foliage quickly and flowers in a few weeks.