When it comes to dealing with powdery mildew, the treatment approach is not very effective in general. Sulphur, neem, baking soda, milk etc all can provide some reasonable effectiveness in preventing or at least slowing down the development of the disease along with other good cultural practises like improving airflow, keeping foliage dry, where possible, etc. but none of them are very effective in my opinion to treat existing disease.
Resistant varieties and Preventative treatment will be the most effective approach when PM is going to be a yearly problem I think
KarenO
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