Handy Hint from Shagmail.com: Non-bleach mildew remover--

1 cup white vinegar

1 cup borax powder

2 cups warm water

Mix ingredients in a bucket or in a spray bottle. Apply to the mildewed area and leave it on for 10 minutes. Rinse.

I haven't tried this, but a couple of years ago I almost asphixiated myself with a spray bottle of bleach solution. I plan to try this method next spring.