Question
I looks like I have a problem with mildew in my garden.
Last 2 years it showed up on some cucumber leafs in the end of the season.
This year it already showed up on zuchini.
My question is : can I do something to the soil after the season to kill it ? and is there anything that I can use now ?

Answer
Mirek:

Mildew is not a soil-borne disease. It is a fungus. Spores can live on plant material left over from the previous year, so the best way to prevent it is to destroy the plant at the end of the season (or earlier if necessary) and clean up and destroy any plant material on the ground.

High humidity promotes the growth of powdery mildew or downy mildew, though each develops at different temperature ranges. You most likely have powdery, as it is common on curcubits.

To avoid it in the future, make sure you have plenty of air circulation around you plants and that they are in full sun. You can treat it now with sulfur, neem oil or a mixture of 1 tbl baking soda to 1 gallon of water. Spray once a week until the the spread of the disease has stopped, or humid conditions have abated. Use as a preventative next year if humid conditions exist.

Elyse