If the plant is decidious the leaves will soon start to fall. Rake them all up and burn them. Remove any mulch from around the base of the plant and burn it too. If the plant is evergreen remove ALL affected limbs and leaves and burn them. Then spray with a copper spray. Replace mulch. In the spring liberally sprinkle horticultural cornmeal all around on the ground and on the plant numerous times during the year and also spray with copper to prophylactically reduce the chance of this stuff recurring.What should i do about it?
Just remember that the spores of both mildew and black spot live in the soil and are spread by splashing water and wind. Keeping this in mind it is probable that every plant in the store has these diseases even though the plants might show zero sign of it.Thanks for the info but I will try to return them.