Neem Oil Recipe

• Neem oil has been used as a home remedy to treat powdery mildew by gardeners. The Neem Foundation recommends adding 30ml of neem oil and 1 ml of biodegradable liquid detergent to one liter of water. Pour the mixture in a spray bottle and apply it to leaf surfaces.
  
  

Considerations

• The U.S. Department of Agriculture has conducted studies on neem oil's effectiveness in controlling powdery mildew on specific ornamental plants. The studies concluded that the oil, indeed, helped control the fungus on tested plants---possibly because it prevented the mildew spores from germinating and/or penetrating the leaves, which it needs to do to survive. More research is needed, according to the University of Connecticut.
  
  

Prevention

• Gardeners can reduce the occurrence of powdery mildew---and thus the need to treat it---by spacing out plants enough to provide for good air circulation. Also avoid placing plants in damp, shady corners, advises the University of Connecticut, as this promotes the disease's growth. Also, some plant varieties, including lilac, dogwood and crab apple, are naturally resistant to powdery mildew.