Well as far as mixing them I wouldn't but there are several different natural fungicides. Potassium Bicarbonate or Sodium Bicarbonate are good. If you can find the Potassium Bicarbonate use that, less of a salt build up. A cup of Horticultural Corn Meal soaked in a gallon of water until the water is nice and milky then spray on as is do not dilute. Neem oil also is a Fungicide but unless you have a really bad fungus problem I wouldn't use it because it also has insect control properties.

Here is the answer to your question on the amount to use:



I wouldn't use more than that because vinegar also acts as a natural herbicide at a high enough concentration.

Chad

To use vinegar as an anti-fungal on humans, you use 1 part vinegar to 9 parts water. I don't know how plants would react to that, but have considered trying it for early blight in tomatoes just to see if it helps. I may try it on one plant just for the heck of it.