How to get rid of mildew on decks and patio furniture
Remove mildew from wood decks and wood patio furniture by sponging them off with a solution of 1 cup ammonia, 1/2 cup white vinegar, and 1/4 cup baking soda mixed in 1 gallon (3.7 liters) water. Keep an old toothbrush on hand to work the solution into corners and other tight spaces.
Source: Readers Digest