There are a number of effective home remedies; I personally have achieved good results with a mixture of milk and water, about in a ratio of 1:8 to 1:10 (~ 200ml per 1.5 L). You can spray it and apply it to the leaves with a cloth during the flowering stage. This should be repeated several times a week. The lactic acid bacteria fight the fungus very effectively. A proper weapon is an emulsion of water, rapeseed oil, and baking powder/soda. It is applied in the same way.