Powdery mildew is one of the most widespread and easily recognised plant diseases. It is most severe in summer and months where the weather is warm and dry, and can affect virtually all kinds of plants. Powdery mildews are characterised by spots or patches of white to grayish, talcum powder-like growth. An interesting fact – it is one of the oldest plant diseases on record! Theophrastis wrote of powdery mildew on roses in 300 B.C.
Powdery mildew fungi seems to be everywhere! The spores form on plant debris and old leaf litter. These spores are carried to your plants by wind, insects and splashing water.
Untreated, powdery mildew inhibits photosynthesis and affects growth as well as fruit and vegetable yield.
If you spot it early, it can be easily treated. Here is a useful treatment you can make yourself:
Mix together 1 tablespoon of baking soda with 3.5L of room temp water, along with 1-2 drops of organic liquid soap (this adheres the solution to the plant). Add a teaspoon of vegetable oil, then shake well to create an emulsion that will help contain the spores (and limit re-infection). Spray in the evening when it’s cooler, and repeat as necessary.
Why does this work? The solution changes the pH balance of the surface of the plant, making it an unsuitable environment for powdery mildew to proliferate.