Powdery mildew is a fungus different from other fungi. Most of them like moist soil conditions, but powdery mildew likes dry soil. Warm days with lots of humidity near the plant and cool nights are perfect for this fungus. Among the most susceptible plants are beans, cucumber, dahlias, fruit trees, grapes, peas, roses and some bluegrass lawns.
Garlic spray using 1 garlic bulb and 4 cups water. Crush bulb of garlic and place it in pan with water. Bring to boil, then turn off the heat. Let it cool and strain out garlic. Pour liquid into a spray bottle and spray affected areas of the plants. Repeat as necessary.
If the disease is left unchecked, the leaves of the affected plants may start to drop, weakening the whole plant. The plant may become stunted and produce low yields.
Try giving the plants a spraying of water in the morning to wash off many of the mildew spores. Prune or pick off affected leaves as soon as you spot white, powdery areas. Clean your tools and dispose of affected plant material away from other plants. Spray infected plants with the baking soda mixture or with garlic.
Beneficial insects are attracted to your garden by coreopsis, feverfew, and sweet alyssum.